This module focuses on the physical layer of the cloud computing reference model.

This module
focuses on physical compute system, its components, and its types. This module also focuses on
storage system architectures. Further, this module focuses on network connectivity and the
types of network communication.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 1
 The physical layer—highlighted in the figure on the slide—is the foundation layer of the cloud
reference model. The process of building a cloud infrastructure is typically initiated with the cloud
service provider setting up the physical hardware resources of the cloud infrastructure.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 2
 The physical layer comprises compute, storage, and network resources, which are the
fundamental physical computing resources that make up a cloud infrastructure. As discussed in
the ‘Introduction to Cloud Computing’ module, the physical resources are typically pooled to serve
multiple consumers.

Physical compute systems host the applications that a provider offers as services to consumers
and also execute the software used by the provider to manage the cloud infrastructure and
deliver services. A cloud provider also offers compute systems to consumers for hosting their
applications in the cloud. Storage systems store business data and the data generated or
processed by the applications deployed on the compute systems. Storage capacity may be offered
along with a compute system or separately (for example, in case of cloud-based backup).
Networks connect compute systems with each other and with storage systems. A network, such
as a local area network (LAN), connects physical compute systems to each other, which enables
the applications running on the compute systems to exchange information. A storage network
connects compute systems to storage systems, which enables the applications to access data
from the storage systems. If a cloud provider uses physical computing resources from multiple
cloud data centers to provide services, networks connect the distributed computing resources
enabling the data centers to work as a single large data center. Networks also connect multiple
clouds to one another—as in case of the hybrid cloud model—to enable them to share cloud
resources and services.

Based on several requirements such as performance, scalability, cost, and so on, a cloud provider
has to make a number of decisions while building the physical layer, including choosing suitable
compute, storage, and network products and components, and the architecture and design of
each system. The subsequent lessons describe various physical components and architectures
that are available to cloud providers to build the physical layer.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 3
 This lesson covers an introduction to compute systems and describes the key components of a
compute system. This lesson also covers the key software deployed on compute systems in a
cloud environment, and the types of compute systems.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 4
 A compute system is a computing platform (hardware, firmware, and software) that runs platform
and application software. Examples of physical compute systems include desktops, laptops,
servers, mobile devices, and so on. A compute system consists of processor(s), memory,
I/O devices, and a collection of software to perform computing operations. The software
includes the operating system (OS), file system, logical volume manager, device drivers,
and so on. The OS may include the other software or they can be installed individually.
The OS manages the physical components and application execution, and provides a user
interface (UI) for users to operate and use the compute system.

In a cloud environment, providers typically deploy x86-based servers or hosts to build the
physical layer. These compute systems execute a provider’s as well as the consumers’ software.
Consumers may deploy their applications entirely on cloud compute systems or may leverage the
cloud for specific scenarios, such as application development and testing, or during peak
workloads. Two or more compute systems are typically combined together into a cluster – a group
of compute systems that function together, sharing certain network and storage resources, and
are viewed as a single system. Compute clusters are typically implemented to provide high
availability and for balancing computing workloads. Compute clustering is covered in detail in the
‘Business Continuity’ module.

A cloud provider typically offers compute systems to consumers in two ways: shared hosting and
dedicated hosting. In shared hosting, the compute systems are shared among multiple
consumers. For example, a provider hosts a consumer’s website on the same compute system as
the websites of other consumers. In dedicated hosting, a provider offers to a consumer dedicated
compute systems that are not shared with any other consumer.

Providers typically install compute virtualization software (hypervisor) on a compute

system and create multiple virtual compute systems, known as virtual machines (VMs), each
capable of running its own OS. In this case, the hypervisor performs compute system
management tasks and allocates the compute system’s resources, such as processor and
memory, dynamically to each VM. The provider allocates the VMs running on a hypervisor to
consumers for deploying their applications. The provider may pre-install an OS on a VM or may
enable the consumers to install an OS of their choice. Compute virtualization is covered in detail
in the ‘Virtual Layer’ module.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 5
 A compute system typically comprises the following key physical hardware components
assembled inside an enclosure:

• Processor: A processor, also known as a Central Processing Unit (CPU), is an integrated circuit
(IC) that executes the instructions of a software program by performing fundamental
arithmetical, logical, and input/output operations. A common processor/instruction set
architecture is the x86 architecture with 32-bit and 64-bit processing capabilities. Modern
processors have multiple cores (independent processing units), each capable of functioning as
an individual processor.

• Random-Access Memory (RAM): The RAM or main memory is a volatile data storage device
internal to a compute system. The RAM holds the software programs for execution and the
data used by the processor.

• Read-Only Memory (ROM): A ROM is a type of semiconductor memory that contains the
boot firmware (that enables a compute system to start), power management firmware, and
other device-specific firmware.

• Motherboard: A motherboard is a printed circuit board (PCB) to which all compute system
components connect. It has sockets to hold components such as the microprocessor chip, RAM,
and ROM. It also has network ports, I/O ports to connect devices such as keyboard, mouse,
and printers, and essential circuitry to carry out computing operations. A motherboard may
additionally have integrated components, such as a graphics processing unit (GPU), a network
interface card (NIC), and adapters to connect to external storage devices.

• Chipset: A chipset is a collection of microchips on a motherboard and it is designed to perform

specific functions. The two key chipset types are Northbridge and Southbridge. Northbridge
manages processor access to the RAM and the GPU, while Southbridge connects the processor
to different peripheral ports, such as USB ports.

(Cont'd)

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 6
 Besides these key components, a compute system may also have components such as a
secondary/persistent storage in the form of a disk drive or a solid state drive, a GPU card, NICs,
and a power supply unit.

Based on the requirements such as the type of cloud services to provide, performance, cost,
expected rate of growth, and so on, a cloud provider has to make multiple important decisions
about the choice of compute system hardware. These decisions include the number of compute
systems to deploy, the number, the type, and the speed of processors, the amount of RAM
required, the motherboard’s RAM capacity, the number and type of expansion slots on a
motherboard, the number and type of I/O cards, installation and configuration effort, and so on.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 7
 On a compute system, a cloud provider deploys software such as the self-service portal, the
application software and platform software that are offered as services (PaaS and SaaS) to
consumers, virtualization software, cloud infrastructure management software, and so on. The
provider also enables consumers to deploy their platform software and business applications on
the compute systems. The slide provides a list and a brief description of the software that are
deployed on compute systems in a cloud environment.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 8
 The compute systems used in building data centers and cloud infrastructure are typically classified
into three categories:

• Tower compute system

• Rack-mounted compute system

• Blade compute system

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 9
 A tower compute system, also known as a tower server, is a compute system built in an upright
enclosure called a “tower”, which is similar to a desktop cabinet. Tower servers have a robust
build, and have integrated power supply and cooling. They typically have individual monitors,
keyboards, and mice. Tower servers occupy significant floor space and require complex cabling
when deployed in a data center. They are also bulky and a group of tower servers generates
considerable noise from their cooling units. Tower servers are typically used in smaller
environments. Deploying a large number of tower servers in large environments may involve
substantial expenditure.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 10
 A rack-mounted compute system, also known as a rack server or an industrial server, is a
compute system designed to be fixed on a frame called a “rack”. A rack is a standardized
enclosure containing multiple mounting slots called “bays”, each of which holds a server in place
with the help of screws. A single rack contains multiple servers stacked vertically in bays, thereby
simplifying network cabling, consolidating network equipment, and reducing floor space use. Each
rack server has its own power supply and cooling unit. A “rack unit” (denoted by U or RU) is a unit
of measure of the height of a server designed to be mounted on a rack. One rack unit is 1.75
inches. A rack server is typically 19 inches (482.6 mm) in width and 1.75 inches (44.45 mm) in
height. This is called a 1U rack server. Other common sizes of rack servers are 2U and 4U. Some
common rack cabinet sizes are 27U, 37U, and 42U.

Typically, a console with a video screen, keyboard, and mouse is mounted on a rack to enable
administrators to manage the servers in the rack. A keyboard, video, and mouse (KVM) switch
connects the servers in the rack to the console and enables the servers to be controlled from the
console. An administrator can switch between servers using keyboard commands, mouse
commands, or touchscreen selection. Using a KVM switch eliminates the need for a dedicated
keyboard, monitor, and mouse for each server and saves space and reduces cable clutter. Some
concerns with rack servers are that they are cumbersome to work with, and they generate a lot of
heat because of which more cooling is required, which in turn increases power costs.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 11
 A blade compute system, also known as a blade server, is an electronic circuit board containing
only core processing components, such as processor(s), memory, integrated network controllers,
storage drive, and essential I/O cards and ports. Each blade server is a self-contained compute
system and is typically dedicated to a single application. A blade server is housed in a slot inside a
blade enclosure (or chassis), which holds multiple blades and provides integrated power supply,
cooling, networking, and management functions. The blade enclosure enables interconnection of
the blades through a high speed bus and also provides connectivity to external storage systems.

The modular design of blade servers makes them smaller, which minimizes floor space
requirements, increases compute system density and scalability, and provides better energy
efficiency as compared to tower and rack servers. It also reduces the complexity of the compute
infrastructure and simplifies compute infrastructure management. It provides these benefits
without compromising on any capability that a non-blade compute system provides. Some
concerns with blade servers include the high cost of a blade system (blade servers and chassis),
and the proprietary architecture of most blade systems due to which a blade server can typically
be plugged only into a chassis from the same vendor.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 12
 This lesson covered the key software that are deployed on a compute system in a cloud
environment. This lesson also covered the key components of a compute system, such as the
processor, RAM, ROM, motherboard, and the chipset. Finally, this lesson covered the three
common types of physical compute systems—tower, rack-mounted, and blade—that are used in
building a cloud infrastructure.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 13
 This lesson covers the common types of persistent storage devices. This lesson also covers
Redundant Array of Independent Disks (RAID) and its use in data protection and storage
performance improvement. Further, this lesson also covers the different types of storage system
architectures, namely block-based, file-based, object-based, and unified storage systems.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 14
 Data created by individuals, businesses, and applications need to be persistently stored
so that it can be retrieved when required for processing or analysis. A storage system is
the repository for saving and retrieving electronic data and is integral to any cloud infrastructure.
A storage system has devices, called storage devices (or storage) that enable the
persistent storage and the retrieval of data. Storage capacity is typically offered to consumers
along with compute systems. Apart from providing storage along with compute systems, a
provider may also offer storage capacity as a service (Storage as a Service), which enables
consumers to store their data on the provider’s storage systems in the cloud. This enables the
consumers to leverage cloud storage resources for purposes such as data backup and long-term
data retention.

A cloud storage infrastructure is typically created by logically aggregating and pooling the storage
resources from one or more data centers to provide virtual storage resources. Cloud storage
provides massive scalability and rapid elasticity of storage resources. The cloud storage
infrastructure is typically shared by multiple tenants or consumers which improves the utilization
of storage resources.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 15
 A magnetic disk is a circular storage medium made of non-magnetic material (typically an alloy)
and coated with a ferromagnetic material. Data is stored on both surfaces (top and bottom) of a
magnetic disk by polarizing a portion of the disk surface. A disk drive is a device that comprises
multiple rotating magnetic disks, called platters, stacked vertically inside a metal or plastic casing.
Each platter has a rapidly moving arm to read from and write data to the disk. Disk drives are
currently the most popular storage medium for storing and accessing data for performance-
intensive applications. Disks support rapid access to random data locations and data can be
written or retrieved quickly for a number of simultaneous users or applications. Disk drives use
pre-defined protocols, such as Advanced Technology Attachment (ATA), Serial ATA (SATA), Small
Computer System Interface (SCSI), Serial Attached SCSI (SAS), and Fibre Channel (FC). These
protocols reside on the disk interface controllers that are typically integrated with the disk drives.
Each protocol has its unique performance, cost, and capacity characteristics.
A solid-state drive (SSD) uses semiconductor-based memory, such as NAND and NOR chips, to
store and retrieve data. SSDs, also known as “flash drives”, deliver the ultra-high performance
required by performance-sensitive applications. These devices, unlike conventional mechanical
disk drives, contain no moving parts and therefore do not exhibit the latencies associated with
read/write head movement and disk rotation. Compared to other available storage devices, SSDs
deliver a relatively high number of input/output operations per second (IOPS) with very low
response times. They also consume less power and typically have a longer lifetime as compared
to mechanical drives. However, flash drives do have the highest cost per gigabyte ($/GB) ratio.
(Cont’d)

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 16
 A magnetic tape is a thin, long strip of plastic film that is coated with a magnetizable material,
such as barium ferrite. The tape is packed in plastic cassettes and cartridges. A tape drive is the
device to record and retrieve data on a magnetic tape. Tape drives provide linear sequential
read/write data access. A tape drive may be standalone or part of a tape library. A tape library
contains one or more tape drives and a storage area where a number of tape cartridges are held
in slots. Tape is a popular medium for long-term storage due to its relative low cost and
portability. Tape drives are typically used by organizations to store large amounts of data,
typically for backup, offsite archiving, and disaster recovery. The low access speed due to the
sequential access mechanism, the lack of simultaneous access by multiple applications, and the
degradation of the tape surface due to the continuous contact with the read/write head are some
key limitations of tape.

An optical disc is a flat, circular storage medium made of polycarbonate with one surface having a
special, reflective coating (such as aluminum). An optical disc drive uses a writing laser to record
data on the disc in the form of microscopic light and dark dots. A reading laser reads the dots,
and generates electrical signals representing the data. The common optical disc types are
compact disc (CD), digital versatile disc (DVD), and Blu-ray disc (BD). These discs may be
recordable or re-writable. Recordable or read-only memory (ROM) discs have Write Once and
Read Many (WORM) capability and are typically used as a distribution medium for applications or
as a means to transfer small amounts of data from one system to another. The limited capacity
and speed of optical discs constrain their use as a general-purpose enterprise data storage
solution. However, high-capacity optical discs are sometimes used as a storage solution for fixed-
content and archival data. Also, some providers of Storage as a Service offer a facility wherein
they copy backup files on encrypted optical discs, if required, and ship them to the
consumers.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 17
 Redundant Array of Independent Disks (RAID) is a storage technology in which multiple disk
drives are combined into a logical unit called a RAID group and data is written in blocks across the
disks in the RAID group. RAID protects against data loss when a drive fails, through the use of
redundant drives and parity. RAID also helps in improving the storage system performance as
read and write operations are served simultaneously from multiple disk drives. For example, if the
RAID group has four disk drives, data is written across all four of them simultaneously, which
provides four times better write performance as compared to using a single drive. Similarly,
during read operation, the data is retrieved simultaneously from each drive.

RAID is typically implemented by using a specialized hardware controller present either on the
host or on the array. The key functions of a RAID controller are management and control of drive
aggregations, translation of I/O requests between logical and physical drives, and data
regeneration in the event of drive failures.

The three different RAID techniques that form the basis for defining various RAID levels are
striping, mirroring, and parity. These techniques determine the data availability and performance
of a RAID group as well as the relative cost of deploying the storage solution. A cloud provider
must select the appropriate RAID levels to meet the requirements of cloud service delivery.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 18
 Striping is a technique to spread data across multiple drives in order to use the drives in parallel
and increase performance as compared to the use of a single drive. Each drive in a RAID group
has a predefined number of contiguously addressable blocks (the smallest individually
addressable unit of storage) called a “strip”. A set of aligned strips that span across all the drives
within the RAID group is called a “stripe”. All strips in a stripe have the same number of blocks.
Although striped RAID provides improved read-write performance, it does not provide any data
protection in case of disk failure.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 19
 Mirroring is a technique in which the same data is stored simultaneously on two different drives,
resulting in two copies of the data. This is called a “mirrored pair”. Even if one drive fails, the data
is still intact on the surviving drive and the RAID controller continues to service data requests
using the surviving drive of the mirrored pair. When the failed disk is replaced with a new disk,
the controller copies the data from the surviving disk of the mirrored pair to the new disk. This
activity is transparent to the host. In addition to providing data redundancy, mirroring enables
fast recovery from disk failure. Since mirroring involves duplication of data, the amount of storage
capacity needed is twice the amount of data being stored. This increases costs because of which
mirroring is typically preferred for mission-critical applications that cannot afford the risk of any
data loss. Mirroring improves read performance because read requests can be serviced by both
disks. However, compared to a single disk and striping, write performance is slightly lower in
mirroring because each write request manifests as two writes on the disk drives.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 20
 Parity is a value derived by performing a mathematical operation on individual strips of data and
stored on a portion of a RAID group. It enables the recreation of missing data in case of a drive
failure. Parity is a redundancy technique that ensures data protection without maintaining a full
set of duplicate data. The RAID controller calculates the parity using techniques such as “bitwise
exclusive or” (XOR). Parity information can be stored on separate, dedicated disk drives or
distributed across the drives in a RAID group. Compared to mirroring, parity implementation
considerably reduces the cost associated with data protection. However, a limitation of parity
implementation is that parity is recalculated every time there is a change in data, which may
affect the performance of the RAID array.

In the figure on the slide, the first four disks, labeled D1 to D4, contain data. The data elements
are 4, 6, 1, and 7. The fifth disk, labeled P, stores the parity information i.e. 18, which is the sum
of the data elements. If one of the drives fails, the missing value can be calculated by subtracting
the sum of the remaining elements from the parity value.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 21
 RAID levels are implementations of the striping, mirroring, and parity techniques. Some RAID
levels use a single technique, while others use a combination of the techniques. The commonly
used RAID levels are RAID 0 – that uses striping, RAID 1 – that uses mirroring, RAID 1+0 – which
is a combination of RAID 1 and RAID 0, and RAID 3, 5, and 6 – that use a combination of striping
and parity.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 22
 Data can be accessed from a compute system (or a compute cluster) through block-level, file-
level, or object-level schemes. External storage systems can be connected to the compute system
directly or over a network. An application on the compute system stores and accesses data using
the underlying infrastructure comprising an OS, a file system, network connectivity, and storage.
In general, an application requests data by specifying the file name and the location. The file
system maps the file attributes to the logical block address (LBA) of the data and sends it to the
storage system. The LBA simplifies addressing by using a linear address to access the block of
data. The storage system converts the LBA to a physical address called the cylinder-head-sector
(CHS) address and fetches the data.

In block-level access, a storage volume (a logical unit of storage composed of multiple blocks,
typically created from a RAID set) is created and assigned to the compute system to house
created file systems. In this case, an application data request is sent to the file system and
converted into a block-level (logical block address) request. This block level request is sent over
the network to the storage system. The storage system then converts the logical block address to
a CHS address and fetches the data in block-sized units.

In file-level access, the file system is created on a separate file server, which is connected to
storage. A file-level request from the application is sent over the network to the file server hosting
the file system. The file system then converts the file-level request into block-level addressing
and sends the request to the storage to access the data.

In object-level access, data is accessed over the network in terms of self-contained objects, each
having a unique object identifier. In this case, the application request is sent to the file system.
The file system communicates to the object-based storage device (OSD) interface, which in turn
sends the object-level request by using the unique object ID over the network to the storage
system. The storage system has an OSD storage component that is responsible for managing the
access to the object on the storage system. The OSD storage component converts the object-
level request into block-level addressing and sends it to the storage to access the data.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 23
 Storage system architecture is a critical design consideration for building cloud infrastructure. A
cloud provider must choose the appropriate storage, and ensure adequate capacity to maintain
the overall performance of the environment. Storage system architectures are based on the data
access methods. The common variants are block-based, file-based, object-based, and unified
storage systems. A unified storage system architecture uses all the three data access methods. A
cloud provider may deploy one or more types of these storage systems to meet the requirements
of different applications.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 24
 A block-based storage system enables the creation and assignment of storage volumes to
compute systems. The compute OS (or hypervisor) discovers these storage volumes as local
drives. A file system can be created on these storage volumes, for example NTFS in a Windows
environment, which can then be formatted and used by applications.

A block-based storage system typically comprises four key components:

• Front-end Controller(s)

• Cache Memory

• Back-end Controller(s)

• Physical disks

The front-end controller provides the interface between the storage system and the compute
systems. Typically, there are redundant controllers in the front-end for high availability, and each
controller contains multiple ports. Each front-end controller has processing logic that executes the
appropriate transport protocol, such as Fibre Channel, iSCSI, or FCoE (discussed later in this
module) for storage connections. Front-end controllers route data to and from a cache memory
via an internal data bus.

The cache is a semiconductor memory where data is placed temporarily to reduce the time
required to service I/O requests from the compute system. The cache improves storage system
performance by isolating compute systems from the mechanical delays associated with disk
drives. Accessing data from the cache typically takes less than a millisecond.

(Cont’d)

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 25
 When a compute system issues a read request, and the data is found in the cache, it is called a
cache hit, and the data is sent directly to the compute system. If the requested data is not found
in the cache, it is called a cache miss and the data must be read from the drive. A write operation
with the cache is implemented in two ways: write-back approach and write-through approach. In
the write-back approach, data of several write operations are placed in the cache and an
acknowledgment for each write is sent to the compute system immediately. Later, the data in the
cache is written to the disk. In the write-through approach, data is placed in the cache and
immediately written to the disk, and an acknowledgment is sent to the compute system.

The back-end controller provides an interface between the cache and the physical disks. The data
from the cache is sent to the back-end and then routed to the destination disks.

Physical disks are connected to ports on the back-end. In some implementations the front-end,
the cache, and the back-end are integrated on a single board referred to as a storage processor
or storage controller.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 26
 A file-based storage system, also known as Network-Attached Storage (NAS), is a dedicated,
high-performance file server having either integrated storage or connected to external storage.
NAS enables clients to share files over an IP network. NAS supports NFS and CIFS protocols to
give both UNIX and Windows clients the ability to share the same files using appropriate access
and locking mechanisms. NAS systems have integrated hardware and software components,
including a processor, memory, NICs, ports to connect and manage physical disk resources, an
OS optimized for file serving, and file sharing protocols. A NAS system consolidates distributed
data into a large, centralized data pool accessible to, and shared by, heterogeneous clients and
application servers across the network. Consolidating data from numerous and dispersed general
purpose servers onto NAS results in more efficient management and improved storage utilization.
Consolidation also offers lower operating and maintenance costs.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 27
 There are two common NAS deployment options: traditional NAS systems (scale-up NAS) and
scale-out NAS systems.

A traditional NAS solution provides the capability to scale the capacity and performance of a single
NAS system. Scaling up a NAS system involves upgrading or adding NAS components and storage
to the NAS system. These NAS systems have a fixed capacity ceiling, and performance is
impacted as the capacity limit is approached.

Scale-out NAS is designed to address the rapidly growing area of unstructured data (data that
does not fit in tables and rows), especially Big Data (data sets whose size or scale break
traditional tools). Scale-out NAS enables the creation of a clustered NAS system by pooling
multiple processing and storage nodes together. The cluster works as a single NAS system and is
managed centrally. The capacity of the cluster can be increased by simply adding nodes to the it.
A node contains common server components and may or may not have disks. As each node is
added to the cluster, it increases the aggregated disk, cache, processor, and network capacity of
the cluster as a whole. Nodes can be non-disruptively added to the cluster when more
performance and capacity is needed. Scale-out NAS creates a single file system that runs on all
nodes in the cluster. As nodes are added, the file system grows dynamically and data is evenly
distributed (or redistributed) to all nodes in the cluster.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 28
 Object-based storage is a way to store file data in the form of objects based on the content and
other attributes of the data rather than the name and location of the file. An object contains user
data, related metadata (size, date, ownership, etc.), and user defined attributes of data
(retention, access pattern, and other business-relevant attributes). The additional metadata or
attributes enable optimized search, retention and deletion of objects. For example, when an MRI
scan of a patient is stored as a file in a NAS system, the metadata is basic and may include
information such as file name, date of creation, owner, and file type. When stored as an object,
the metadata component of the object may include additional information such as patient name,
ID, attending physician’s name, and so on, apart from the basic metadata.

Each object stored in the object-based storage system is identified by a unique identifier called
the object ID. The object ID allows easy access to objects without having to specify the storage
location. The object ID is generated using specialized algorithms (such as a hash function) on the
data and guarantees that every object is uniquely identified. Any changes in the object, like user-
based edits to the file, results in a new object ID. This makes object-based storage a preferred
option for long term data archiving to meet regulatory or compliance requirements. The object-
based storage system uses a flat, non-hierarchical address space to store data, providing the
flexibility to scale massively. Cloud service providers leverage object-based storage systems to
offer Storage as a Service because of its inherent security, scalability, and automated data
management capabilities. Object-based storage systems support web service access via REST and
SOAP.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 29
 The object-based storage system has three key components: nodes, internal (private) network,
and storage. The object-based storage system is composed of one or more nodes. In this
context, a node is a server that runs the object-based storage operating environment
and provides services to store, retrieve, and manage data in the system. The object-
based storage system node has two key services: metadata service and storage service.
The metadata service is responsible for generating the object ID from the contents of a
file. It also maintains the mapping between the object IDs and the file system
namespace. The storage service manages a set of drives on which the data is stored. The
nodes connect to the storage via an internal network. The internal network provides both
node-to-node connectivity and node-to-storage connectivity. The application server
accesses the object-based storage node to store and retrieve data over an external
network. In some implementations, the metadata service might reside on the application
server or on a separate server.

Object-based storage provides the capability to automatically detect and repair corrupted
objects, and to alert the administrator of any potential problem. It also provides on-
demand reporting and event notification. Some object-based storage systems support
storage optimization techniques such as single instance storage, where only one instance
of an object is stored, thereby optimizing the usable capacity.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 30
 Unified storage or multiprotocol storage has emerged as a solution that consolidates block, file,
and object-based access within one storage platform. It supports multiple protocols such as CIFS,
NFS, iSCSI, FC, FCoE, REST, and SOAP for data access. Such a unified storage system is managed
using a single interface. A unified storage system consists of the following key components:
storage controller, NAS head, OSD node, and storage. The storage controller, NAS head, and OSD
node may be present either separately or be part of a single unit.

The storage controller provides block-level access to compute systems through various protocols.
It contains front-end ports for direct block access. The storage controller is also responsible for
managing the back-end storage pool in the storage system. The controller configures storage
volumes and presents them to NAS heads and OSD nodes, as well as to the compute systems.

A NAS head is a dedicated file server that provides file access to NAS clients. The NAS head
connects to the storage via the storage controller. The system usually has two or more NAS heads
for redundancy. The NAS head configures the file systems on assigned volumes, creates NFS,
CIFS, or mixed shares, and exports the shares to the NAS clients.

The OSD node also accesses the storage through the storage controller. The volumes assigned to
the OSD node appear as physical disks. These disks are configured by the OSD nodes, enabling
them to store object data.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 31
 This lesson covered the common types of persistent data storage devices. This lesson also
covered the different RAID techniques (striping, mirroring, and parity) used for data protection
and for improving storage performance. Finally, this lesson covered the different data access
methods and the storage system architectures based on them, including block-based, file-based,
object-based, and unified storage systems.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 32
 This lesson covers the types of network communication and describes compute-to-compute
communication. This lesson also covers compute-to-storage communication via a storage area
network (SAN) and the classification of SAN. Further, this lesson covers inter-cloud
communication.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 33
 A network establishes communication paths between the devices in an IT infrastructure. Devices
that are networked together are typically called “nodes”. A network enables information exchange
and resource sharing among a large numbers of nodes spread across geographic regions and over
long distances. A network may also be connected to other networks to enable data transfer
between nodes.

Cloud providers typically leverage different types of networks supporting different network
protocols and transporting different classes of network traffic. As established in the discussion of
fundamental cloud characteristics, cloud consumers require reliable and secure network
connectivity to access cloud services. A provider connects the cloud infrastructure to a network
enabling clients (consumers) to connect to the cloud over the network and use cloud services. For
example, in an on-premise private cloud, the clients typically connect to the cloud infrastructure
over an internal network, such as a LAN. In case of a public cloud, the cloud infrastructure
connects to an external network, typically the Internet, over which consumers access cloud
services.

Cloud service providers may also use IT resources at one or more data centers to provide cloud
services. If multiple data centers are deployed, the IT resources from these data centers may be
logically aggregated by connecting them over a wide area network (WAN). This enables both
migration of cloud services across data centers and provisioning cloud services using resources
from multiple data centers. Also, multiple clouds may be inter-connected over a WAN to enable
workloads to be moved or distributed across clouds. This scenario was covered in the
‘Introduction to Cloud Computing’ module as part of the discussion on cloud bursting in a hybrid
cloud environment.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 34
 Networks in a cloud environment may be classified into various types based on attributes such as
communication protocol, topology, transport medium, and so on. Generally network
communication may be categorized into: compute-to-compute communication, compute-to-
storage communication, and inter-cloud communication.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 35
 Compute-to-compute communication typically uses protocols based on the Internet Protocol (IP).
Each physical compute system (running an OS or a hypervisor) is connected to the network
through one or more physical network cards, such as a network interface controller (NIC).
Physical switches and routers are the commonly-used interconnecting devices. A switch enables
different compute systems in the network to communicate with each other. A router enables
different networks to communicate with each other. The commonly-used network cables are
copper cables and optical fiber cables. The figure on the slide shows a network (Local Area
Network – LAN or Wide Area Network – WAN) that provides interconnections among the physical
compute systems. The cloud provider has to ensure that appropriate switches and routers, with
adequate bandwidth and ports, are in place to ensure the required network performance.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 36
 A network of compute systems and storage systems is called a storage area network (SAN). A
SAN enables the compute systems to access and share storage systems. Sharing improves the
utilization of the storage systems. Using a SAN facilitates centralizing storage management, which
in turn simplifies and potentially standardizes the management effort.

SANs are classified based on protocols they support. Common SAN deployments types are Fibre
Channel SAN (FC SAN), Internet Protocol SAN (IP SAN), and Fibre Channel over Ethernet SAN
(FCoE SAN).

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 37
 An FC SAN is a high speed, dedicated network of compute systems and shared storage systems
that uses Fibre Channel (FC) protocol to transport data, commands, and status information
between the compute and the storage systems. The FC protocol primarily implements the Small
Computer System Interface (SCSI) command set over FC, although it also supports other
protocols such as Asynchronous Transfer Mode (ATM), Fibre Connection (FICON), and IP. SCSI
over FC overcomes the distance and accessibility limitations associated with traditional, direct-
attached SCSI protocol systems. FC protocol provides block-level access to the storage systems.
It also provides a serial data transfer interface that operates over both copper and optical fiber
cables. Technical committee T11, a committee within International Committee for Information
Technology Standards (INCITS), is responsible for FC interface standards. The latest FC
implementations of 16 Gigabit Fibre Channel (GFC) offers data transfer speeds up to 16 Gbps. The
FC architecture is highly scalable, and theoretically a single FC SAN can accommodate
approximately 15 million nodes.

Note: The term “Fibre” refers to the protocol, whereas the term “fiber” refers to the medium.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 38
 The key FC SAN components include network adapters, cables and connectors, and
interconnecting devices.

Each node requires one or more network adapters to provide a physical interface for
communicating with other nodes. Examples of network adapters are FC host bus adapters (HBAs),
and storage system front-end adapters. An FC HBA has SCSI-to-FC processing capability. It
encapsulates OS (or hypervisor) storage I/Os (usually SCSI I/O) into FC frames before sending
the frames to FC storage systems over an FC SAN.

FC SAN predominantly uses optical fiber to provide physical connectivity between nodes. Copper
cables might be used for shorter distances. A connector may attach at the end of a cable to
enable swift connection and disconnection of the cable to and from a port.

FC switches and directors are the interconnecting devices commonly used in an FC SAN to forward
data from one physical switch port to another. Directors are high-end switches with a higher port
count and better fault-tolerance capabilities than smaller switches (also known as “departmental”
switches). Switches are available with a fixed port count or with a modular design. In a modular
switch, the port count is increased by installing additional port cards into empty slots. Modular
switches enable online installation of port cards. The architecture of a director is usually modular,
and its port count is increased by inserting line cards or blades to the director’s chassis.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 39
 A fabric is created with an FC switch (or an FC director) or a network of switches that enable all
nodes to connect to each other and communicate. Each switch in a fabric contains a unique
domain identifier (ID), which is part of the fabric’s addressing scheme. Each network adapter and
network adapter port in the FC environment has a globally unique 64-bit identifier called the
World Wide Name (WWN). Unlike an FC address, which is assigned dynamically, a WWN is a static
name. WWNs are burned into the hardware or assigned through software. An FC network adapter
is physically identified by a World Wide Node Name (WWNN), and an FC adapter port is physically
identified by a World Wide Port Name (WWPN). For example, a dual-port FC HBA has one WWNN
and two WWPNs. Further, each FC adapter port in a fabric has a unique 24-bit FC address for
communication.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 40
 A port in a switched fabric can be one of the following types:

• N_Port is an end-point in the fabric. This port is also known as the node port (or FC
adapter port). Typically, it is a compute system port (on an FC HBA) or a storage
system port connected to a switch in a fabric.

• E_Port is a switch port that forms a connection between two FC switches. This port is
also known as an expansion port. The E_Port on an FC switch connects to the E_Port
of another FC switch in the fabric through ISLs.

• F_Port is a port on a switch that connects an N_Port. It is also known as a fabric port.

• G_Port is a generic port on some vendors’ switches. It can operate as an E_Port or an

F_Port and determines its functionality automatically during initialization.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 41
 Zoning is an FC switch function that enables node ports within the fabric to be logically
segmented into groups and to communicate with each other within the group. Whenever a
change takes place in the fabric, the fabric sends a registered state change notification (RSCN) to
the nodes in the fabric. If zoning is not configured, the RSCNs are received by all nodes in the
fabric. This includes nodes that are not impacted by the change, resulting in increased fabric-
management traffic. For a large fabric, the amount of FC traffic generated due to this process can
be significant and might impact the compute-to-storage data traffic. Zoning helps to limit the
number of RSCNs in a fabric. In the presence of zoning, a fabric sends the RSCNs to only those
nodes in the zone where the change has occurred.

Both node ports and switch ports can be members of a zone. A port or node can be a member of
multiple zones. Nodes distributed across multiple switches in a fabric may also be grouped into
the same zone.

Single-initiator-single-target zoning is considered as an industry best practice to configure zones.

In an FC SAN, the HBA ports and the storage system ports are called initiator ports and target
ports respectively. A single-initiator-single-target zone consists of one initiator port and one
target port. Single-initiator-single-target zoning eliminates unnecessary compute-to-compute
interaction and minimizes RSCNs. Single-initiator-single-target zoning in a large fabric leads to
configuring a large number of zones and more administrative actions. However, this practice
improves the FC SAN performance and reduces the time to troubleshoot FC SAN-related
problems.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 42
 Zoning can be categorized into three types: WWN zoning, port zoning, and mixed zoning.

WWN zoning uses WWNs to define zones. The zone members are the unique WWPN addresses of
the ports in HBA and its targets (storage systems). A major advantage of WWN zoning is its
flexibility. WWN zoning allows nodes to be moved to another switch port in the fabric and to
maintain connectivity to their zone partners without having to modify the zone configuration. This
is possible because the WWN is static to the node port.

Port zoning uses the switch port identifier to define zones. In port zoning, access to data is
determined by the physical switch port to which a node is connected. The zone members are the
port identifier (switch domain ID and port number) to which an HBA and its targets are
connected. If a node is moved to another switch port in the fabric, then zoning must be modified
to allow the node, in its new port, to participate in its original zone. However, if an HBA or a
storage system port fails, an administrator just has to replace the failed device without changing
the zoning configuration.

Mixed zoning combines the qualities of both WWN zoning and port zoning. Using mixed zoning
enables a specific node port to be tied to the WWN of a node.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 43
 IP SAN uses the Internet Protocol (IP) for the transport of storage traffic. It transports block I/O
over an IP-based network. IP is a mature technology, and using IP SAN as a storage networking
option provides several advantages. Cloud providers may have an existing IP-based network
infrastructure, which could be used for storage networking. Leveraging an existing IP-based
network therefore may be a more economical option than investing in building a new FC SAN
infrastructure. In addition, many robust and mature security options are available for IP networks.
Many long-distance, disaster recovery (DR) solutions already leverage IP-based networks.
Therefore, with IP SAN, providers can extend the geographical reach of their storage
infrastructure.

Two primary protocols that leverage IP as the transport mechanism for block-level data
transmission are Internet SCSI (iSCSI) and Fibre Channel over IP (FCIP).

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 44
 iSCSI encapsulates SCSI commands and data into IP packets. These IP packets are transported
over an IP-based network. iSCSI network components include:

• iSCSI initiators such as a software iSCSI adapter and an iSCSI HBA

• iSCSI targets such as a storage system with iSCSI port or an iSCSI gateway

• IP-based network

An iSCSI initiator sends commands and associated data to a target and the target returns data
and responses to the initiator. The software iSCSI adapter is an OS (or hypervisor) kernel-
resident software that uses an existing NIC of the compute system to emulate an iSCSI initiator.
An iSCSI HBA has a built-in iSCSI initiator and is capable of providing performance benefits over
software iSCSI adapters by offloading the entire iSCSI and TCP/IP processing from the processor
of the compute system. If an iSCSI-capable storage system is deployed, then an iSCSI initiator
can directly communicate with the storage system over an IP-based network. This type of iSCSI
implementation is called native iSCSI. Otherwise, in an iSCSI implementation that uses a storage
system with only FC ports, an iSCSI gateway is used. This gateway device performs the
translation of IP packets to FC frames and vice versa, thereby bridging the connectivity between
the IP and the FC environments. This type of iSCSI implementation is called bridged iSCSI. The
figure on the slide shows both native and bridged iSCSI implementations.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 45
 A unique worldwide iSCSI identifier, known as an iSCSI name, identifies the initiators and the
targets within an iSCSI network to facilitate communication. The unique identifier can be a
combination of the names of the department, application, or manufacturer, serial number, asset
number, or any tag that can be used to recognize and manage the devices. The two types of
iSCSI names that are commonly used are:

• iSCSI Qualified Name (IQN): An organization must own a registered domain name to
generate iSCSI Qualified Names. This domain name does not need to be active or resolve to an
address. It just needs to be reserved to prevent other organizations from using the same
domain name to generate iSCSI names. A date is included in the name to avoid potential
conflicts caused by the transfer of domain names. An example of an IQN is iqn.2014-
02.com.example:optional_string. The optional_string provides a serial number, an asset
number, or any other device identifiers. An iSCSI Qualified Name enables storage
administrators to assign meaningful names to iSCSI devices, and therefore, manage those
devices more easily.

• Extended Unique Identifier (EUI): An EUI is a globally unique identifier based on the IEEE
EUI-64 naming standard. An EUI is composed of the “eui” prefix followed by a 16-character
hexadecimal name, such as eui.0300732A32598D26.

In either format, the allowed special characters are dots, dashes, and blank spaces.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 46
 FCIP is an encapsulation of FC frames into IP packets. FCIP is a tunneling protocol that enables
distributed FC SAN islands to be interconnected over the existing IP-based networks. This enables
transporting FC data between disparate FC SANs that may be separated by a long distance. In an
FCIP environment, an FCIP entity such as an FCIP gateway is deployed at either end of the tunnel
between two FC SAN islands, as shown in the figure on the slide. An FCIP gateway encapsulates
FC frames into IP packets and transfers them to the remote gateway through the tunnel. The
remote FCIP gateway decapsulates the FC frames from the IP packets and sends the frames to
the remote FC SAN. FCIP is extensively used in disaster recovery implementations in which data is
replicated to storage located at a remote site.

An FCIP implementation is capable of merging interconnected fabrics into a single fabric. In a

merged fabric, the fabric service related traffic travels between interconnected FC SANs through
the FCIP tunnel. However, only a small subset of nodes at either end of the FCIP tunnel requires
connectivity across the tunnel. Thus, the majority of FCIP implementations today use some
switch-specific features to prevent the fabrics from merging and also restrict the nodes that are
allowed to communicate across the fabrics.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 47
 FCoE SAN is a converged enhanced Ethernet (CEE) network that is capable of transporting FC
data along with regular Ethernet traffic over high speed (such as 4 Gbps, 8 Gbps, 10 Gbps, or
higher) Ethernet links. It uses the FCoE protocol that encapsulates FC frames into Ethernet
frames. FCoE is based on an enhanced Ethernet standard that supports Data Center Bridging
(DCB) functionalities. DCB ensures lossless transmission of FC traffic over Ethernet.

FCoE SAN provides the flexibility to deploy the same network components for transferring both
compute-to-compute traffic and FC storage traffic. This helps in reducing the complexity of
managing multiple discrete network infrastructures. FCoE SAN uses multi-function network
adapters and switches. Therefore, FCoE reduces the number of adapters, cables, and switches,
along with power and space consumption required in a data center.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 48
 An FCoE SAN consists of converged network adapters (CNAs), FCoE switches, cables, and FCoE
storage ports.

A CNA is a physical adapter that provides the functionality of both NIC and FC HBA in a single
device. It consolidates both FC traffic and regular Ethernet traffic on a common Ethernet
infrastructure. CNAs connect compute systems to FCoE switches. They are responsible for
encapsulating FC traffic onto Ethernet frames and forwarding them to FCoE switches over CEE
links.

Instead of CNA, a software FCoE adapter may also be used. A software FCoE adapter is software
on the compute system that performs FCoE processing. FCoE processing consumes compute
system processor cycles. With software FCoE adapters, the compute system implements FC
protocol in software that handles SCSI to FC processing. The software FCoE adapter performs FC
to Ethernet encapsulation. Both FCoE traffic (Ethernet traffic that carries FC data) and regular
Ethernet traffic are transferred through supported NICs on the compute system.

The figure on the slide shows an FCoE implementation that consolidates both FC SAN traffic and
LAN (Ethernet) traffic on a common Ethernet infrastructure.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 49
 An FCoE switch has the functionalities of both an Ethernet switch and an FC switch. It has a Fibre
Channel Forwarder (FCF), an Ethernet Bridge, and a set of ports that can be used for FC, Ethernet
or FCoE connectivity. The function of the FCF is to encapsulate the FC frames received from an
existing FC SAN into the Ethernet frames, and also to decapsulate the Ethernet frames received
from the Ethernet Bridge to the FC frames.

Some vendors offer FCoE ports in their storage systems. These storage systems connect directly
to FCoE switches. The FCoE switches form FCoE fabrics between compute and storage systems
and provide end-to-end FCoE support. The figure on the slide shows an FCoE implementation with
an FCoE-capable storage system.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 50
 The cloud tenets of rapid elasticity, resource pooling, and broad network create a sense of
availability of limitless resources in a cloud infrastructure that can be accessed from any location
over a network. However a single cloud does not have an infinite number of resources. A cloud
that does not have adequate resources to satisfy service requests from clients, may be able to
fulfill the requests if it is able to access the resources from another cloud. For example, in a
hybrid cloud scenario, a private cloud may access resources from a public cloud during peak
workload periods. There may be several combinations of inter-cloud connectivity as depicted in
the figure on the slide. Inter-cloud connectivity enables clouds to balance workloads by accessing
and using computing resources, such as processing power and storage resources from other cloud
infrastructures. The cloud provider has to ensure network connectivity of the cloud infrastructure
over a WAN to the other clouds for resource access and workload distribution.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 51
 This lesson covered the types of network communication, compute-to-compute communication,
and compute-to-storage communication over a storage area network (SAN). This lesson also
covered the classification of SAN—FC SAN, IP SAN, and FCoE SAN—and described the components
and architecture of each. Finally, this lesson covered inter-cloud communication.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 52
 The Concepts in Practice section covers EMC VMAX, EMC VNX, EMC ECS Appliance, EMC Isilon,
EMC Atmos, EMC XtremIO, and EMC Connectrix.

Note:

For the latest information on EMC products, visit www.emc.com.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 53
 The EMC VMAX family of storage arrays is a full line of high-end enterprise storage platforms
from EMC. The VMAX series provides block-based storage that delivers enterprise storage with
scalability, performance, and availability to meet the business requirements. The VMAX series is
an innovative platform built around a scalable Virtual Matrix architecture to support the future
storage growth demands of virtual data centers and cloud environments. It also supports multiple
protocols for host connectivity. VMAX storage systems provide business continuity solution by
supporting various local and remote replications.

The EMC VNX family is a group of products that provide a unified storage platform that
consolidates block, file, and object access into one solution. The VNX series is built for small to
medium-sized businesses and enterprises. It enables organizations to dynamically grow, share,
and manage multi-protocol file systems and multi-protocol block storage access. The VNX
operating environment enables Windows and UNIX/Linux users to share files using NFS and CIFS.
It also supports FC, iSCSI, and FCoE access.

EMC ECS Appliance is a hyper-scale storage infrastructure that provides universal

protocol support in a single, highly-available platform for block, file, object, and Hadoop
Distributed File System (HDFS) storage. ECS Appliance enables cloud providers to deliver
competitive cloud storage services at scale. It provides geo-efficient protection, multi-
tenancy, self-service portal, and detailed metering capabilities and enables scaling to
Exabyte levels. ECS provides a single platform for all web, mobile, Big Data, and social
media applications. There are two types of data services within ECS: Block Data Services
and Unstructured Data Services that support unstructured, block, and mixed use cases.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 54
 EMC Isilon is a scale-out NAS storage product family powered by the OneFS operating
environment. Isilon enables pooling multiple nodes together to construct a clustered NAS
system. OneFS is the operating environment that creates a single file system that spans across all
nodes in an Isilon cluster. EMC Isilon provides the capability to manage and store large (petabyte-
scale), high-growth data in a single system with the flexibility to meet a broad range of
performance requirements.

EMC Atmos is a cloud storage platform for enterprises and service providers to deploy public,
private, or hybrid cloud storage. It enables to store, manage, and protect globally distributed,
unstructured content at scale. Atmos is a scale-out object architecture that stores data as objects
with the associated metadata. It enables storage to be scaled out without the need to rewrite
applications. Some of the key cloud features of Atmos include a global namespace, REST API-
driven storage, multi-tenancy, self-service, and metering and chargeback.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 55
 EMC XtremIO is an all-flash, block-based, scale-out enterprise storage array that provides
substantial improvements to I/O performance. It is purpose-built to leverage flash media and
delivers new levels of real-world performance, administrative ease, and advanced data services
for applications. It uses a scale-out clustered design that grows capacity and performance linearly
to meet any requirement. XtremIO arrays are created from building blocks called "X-Bricks" that
are each a high-availability, high-performance, fully active/active storage system with no single
point of failure. XtremIO's powerful operating system, XIOS, manages the XtremIO storage
cluster. XIOS ensures that the system remains balanced and always delivers the highest levels of
performance with no administrator intervention. XtremIO helps the administrators to become
more efficient by enabling system configuration in a few clicks, provisioning storage in seconds,
and monitoring the environment with real-time metrics.

The EMC Connectrix family is a group of networked storage connectivity products. EMC offers
the following connectivity products under the Connectrix brand:

• Enterprise directors: Ideal for large enterprise connectivity. Offer high port density and
high component redundancy. Deployed in high-availability or large-scale environments

• Departmental switches: Designed to meet workgroup-level, department-level, and

enterprise-level requirements. Provide high availability through features such as non-
disruptive software and port upgrade, and redundant and hot-swappable components

• Multi-purpose switches: Support various protocols such as FC, iSCSI, FCIP, FCoE, and FICON.
Include FCoE switches, FCIP gateways, and iSCSI gateways. Multiprotocol capabilities offer
many benefits, including long-distance SAN extension, greater resource sharing, and simplified
management.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 56
 This module covered the key components of a compute system and the common types of physical
compute systems: tower, rack-mounted, and blade. This module also covered the common types
of persistent storage devices, the different RAID techniques (striping, mirroring, and parity), and
the types of storage system architectures: block-based, file-based, object-based, and unified
storage systems. Finally, this module covered compute-to-compute communication, compute-to-
storage communication (SAN), and SAN classification: FC SAN, IP SAN, and FCoE SAN. Finally,
this module covered inter-cloud communication.

Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 57
Copyright 2014 EMC Corporation. All rights reserved. Module: Physical Layer 58