Module: Physical Layer

Upon completion of this module, you should be able to:

• Describe compute system components and types
• Describe storage system architectures
• Describe network connectivity and the types of network
communication

Module: Physical Layer

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Cloud Computing Reference Model
Physical Layer

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Physical Layer Overview
• The physical layer comprises physical
compute, storage, and network resources
• Compute systems execute software of
providers and consumers
• Storage systems store business and
application data
• Networks connect compute systems with
each other and with storage systems
– Networks also connect multiple data centers
or multiple clouds to one another

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 Lesson: Compute System
This lesson covers the following topics:
• Key components of a compute system
• Software deployed on compute systems
• Types of compute systems

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Introduction to Compute System
• A computing platform (hardware, firmware, and software) that
runs platform and application software
– Executes the provider’s as well as the consumers’ software
– Typically x86-based servers or hosts
• Compute systems are provided to consumers in two ways:
– Shared hosting: Multiple consumers share compute systems
– Dedicated hosting: Individual consumers have dedicated compute
systems
• Typically providers use compute virtualization and offer
compute systems in the form of virtual machines

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Key Components of a Compute System

• An IC that executes software programs by performing

Processor arithmetical, logical, and input/output operations

• A volatile data storage device containing the programs for

Random-Access Memory execution and the data used by the processor

• A semiconductor memory containing boot, power management,

Read-Only Memory and other device-specific firmware

• A PCB that holds the processor, RAM, ROM, network and I/O
Motherboard ports, and other integrated components, such as GPU and NIC

• A collection of microchips on a motherboard to manage specific

Chipset functions, such as processor access to RAM and to peripheral
ports

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Software Deployed on Compute Systems

Self-service portal • Enables consumers to view and request cloud services

Platform software • Includes the software that the provider offers through PaaS

Application software • Includes the applications that the provider offers through SaaS

Virtualization software • Enables resource pooling and creation of virtual resources

• Enables a provider to manage the cloud infrastructure and

Cloud management software services

• Includes a consumer’s platform software and business

Consumer software applications

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Types of Compute Systems
• Tower compute system
• Rack-mounted compute system
• Blade compute system

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Tower Compute System
• Built in an upright enclosure called a “tower”
• Has integrated power supply and cooling
• A group of towers occupies significant floor
space, requires complex cabling, and
generates noise from cooling units
• Deploying in large environments may involve
substantial expenditure

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Rack-mounted Compute System
• Designed to be fixed on a frame called a
“rack”
– A rack is a standardized enclosure with
mounting slots for vertically stacking compute
systems
• Simplifies network cabling, consolidates
network equipment, and reduces floor space
use
• Administrators may use a console mounted
on the rack to manage the compute systems

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Blade Compute System
• Comprises an electronic circuit board with
only the core processing components
• Multiple blades are housed in a blade chassis
– The chassis provides integrated power supply,
cooling, networking, and management
• Blades are interconnected via a high speed
bus
• Modular design increases compute system
density and scalability

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 Lesson Summary
During this lesson the following topics were covered:
• Key components of a compute system
• Software deployed on compute systems
• Types of compute systems: tower, rack-mounted, and blade

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 Lesson: Storage System
This lesson covers the following topics:
• Types of storage devices
• Redundant Array of Independent Disks (RAID)
• Storage system architectures

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Introduction to Storage System
• A storage system is the repository for saving and retrieving
electronic data
• Providers offer storage capacity along with compute systems,
or as a service
– Storage as a Service enables data backup and long-term data
retention
• Cloud storage provides massive scalability and rapid elasticity
of storage resources
• Typically, a provider uses virtualization to create storage pools
that are shared by multiple consumers

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Types of Storage Devices
• Stores data on a circular disk with a ferromagnetic coating
Magnetic disk drive • Provides random read/write access
• Most popular storage device with large storage capacity

• Stores data on a semiconductor-based memory

Solid-state (flash) drive • Very low latency per I/O, low power requirements, and very high
throughput

• Stores data on a thin plastic film with a magnetic coating

Magnetic tape drive • Provides only sequential data access
• Low-cost solution for long term data storage

• Stores data on a polycarbonate disc with a reflective coating

Optical disc drive • Write Once and Read Many capability: CD, DVD, BD
• Low-cost solution for long-term data storage

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Redundant Array of Independent Disks (RAID)
RAID
A storage technology in which data is written in blocks across multiple disk
drives that are combined into a logical unit called a RAID group.

• Improves storage system performance by serving I/Os from

multiple drives simultaneously
• Provides data protection against drive failures
• Three key techniques used for RAID: striping, mirroring, and
parity

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RAID Technique: Striping
Striping
A RAID technique to spread data across multiple drives in order to use the
drives in parallel.

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RAID Technique: Mirroring
Mirroring
A RAID technique to store the same data simultaneously on two different
drives, yielding two copies of the data.

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RAID Technique: Parity
Parity
A RAID technique to protect striped data from drive failure by performing a
mathematical operation on individual strips and storing the result on a
portion of the RAID group.

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 Parity
D1 value 4
D2 value 6
D3 value 1
D4 value 7
Total =18
DP value 18 as Parity
If D2 is missing then 18 – (4 + 1 +7) = 6

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Common RAID Levels

RAID 0 • Striped set with no fault tolerance

RAID 1 • Disk mirroring

RAID 1+0 • Nested RAID (striping and mirroring)

RAID 3 • Striped set with parallel access and a dedicated parity disk

RAID 5 • Striped set with independent disk access and distributed parity

• Striped set with independent disk access and dual distributed

RAID 6 parity

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Data Access Methods

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Storage System Architecture
• Storage system architectures are based on the data access
methods
• Common storage system options are:
– Block-based
– File-based
– Object-based
– Unified

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Block-based Storage System
• Enables creating and assigning storage volumes to compute
systems
– Compute system discovers the volumes as local drives
– Required file system can be created on the volumes

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File-based Storage System
• A dedicated, high
performance file server with
storage (also known as
Network-attached Storage)
• Enables clients to share files
over an IP network
– Supports data sharing for
UNIX and Windows users
• Uses a specialized OS that is
optimized for file I/O

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Object-based Storage System
• Stores file data in the form
of objects based on data
contents and attributes
– Uses a flat, non-
hierarchical address
space
• Object contains user data,
related metadata, and
user-defined attributes
– Objects are uniquely
identified using object ID

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Unified Storage System

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Inter-cloud Communication

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