Hard Disk Drives (HDD)
1. Introducing the Hard Disk Drive
2. Drive Interface
a. IDE
b. EIDE
c. SCSI
d. Serial ATA
3. Choosing the right disk
4. Measure the Hard Drive Performance (From A+ Book)
a. Maximum Data Transfer Rate
b. Read and Write Seek Times
c. Latency
d. Rotational Speed
5. Installing Hard Drives (From A+ Book)
a. Step 1 : Set the jumpers
b. Step 2 : Put the Drive in the Bay
c. Step 3 : Connect it to the motherboard
d. Step 4 : Connect it to the Power Supply
e. Step 5 : Set up the BIOS
6. Preparing a Hard Drive for Use
a. Starting the PC
b. Partitioning
c. Disk Formatting
7. Common Hard Drive Problems
a. BIOS does not the drive
b. No drive letter at Command Prompt or in My Computer
c. Can’t see Files on Drive
d. Data Error or Problems with a specific File
Chapter 1 : Introducing the Hard Disk Drive
The PCs have moved from being pure computing devices for developers to
entertainment and Internet browsing machines. Today, an average computer user stores
graphics, music, movies, downloads, besides documents and spreadsheets. With latest
operating systems and applications occupying up to 800 MB, 2 GB hard disk drives,
which used to be the norm sometime ago, are simply not enough.
Fortunately, advances in disk storage technology have kept pace with the
increasingly bloated sizes of applications and increasing requirements of users. Today a
20 GB hard disk can be bought for approximately the same price that a 2 GB drive sold a
year ago, and it is not uncommon to find users opting for high-capacity devices even for
home use. In fact, it makes more sense to buy higher capacity hard disks, especially
when you consider the fact that the price difference between, say, a 20 GB drive and a 10
GB drive is negligible when compared to the increased capacity that you are getting.
Hard disks are also a vital part of servers, where speed, reliability, and capacity
assume a totally new meaning altogether. File servers, Web servers and data mining
applications, which are running mission critical tasks, can even have multiple hard drives
and handle multiple users at the same time.
Therefore, depending on the segment for which hard disks are used, there can be
two broad classifications of hard drives—IDE and SCSI.
The former is generally used by all desktop users, while the latter serves the
server market. Though, both IDE and SCSI can have different sub-categorisations, (see
‘The hard disk interface’), the objective of this test is to identify the best performer and
the best value hard disk drives for general home and office use, and also for high-end use.
With high-capacity hard disks now becoming fairly common even with home users, we
have not divided hard drives according to capacity, but according to the interface.
Chapter 2 : The hard disk interface
The drive interface is the language or protocol a drive uses to communicate with a host
computer or network. These can be of the following types:
IDE Drives
IDE (Integrated Drive Electronics) Drives are the default drive on most modern
computers. IDE systems put most of the electronics on the drive itself. The encoding and
decoding and the control signals are done on the circuit board under the drive. The
adapter card relays the signals from the drive to the computer. IDE and EIDE (Enhanced
IDE) interfaces come as standard, ATA, Fast ATA-2, ATA-3 Ultra DMA, ATA66.
IDE and EIDE style hard drives connect to the computer usually via a built-in connector
on the motherboard. As many as 2 drives can be connected to a single 2 headed cable. A
computer can have a total of 2 IDE / EIDE hard drive cables connected. The first cable is
the motherboard connector and the hard drives attached to it are referred to as primary.
The second set is called the secondary. Each of the cables has its own designation of
Master and Slave.
IDE as an interface had certain limitations. Disks larger than 528 MB could not be
accessed and data was delivered on an ISA bus, resulting in low transfer rates. These
limitations were overcome in EIDE or Enhanced IDE. In this implementation, data is
delivered on a PCI bus and at the same time, EIDE also supports larger disk sizes.
EIDE Drives
EIDE means Enhanced IDE, which does not carry some of the limitations of the original
IDE interface. You can put as many as four devices on one controller. EIDE even allows
non-disk devices to be used, auch as CD-ROMS. The original IDE allowed only hard
drives. EIDE allows the use of much higher capacity drives. It allows a transfer rate of
around 11.1 MB per second, which is much faster than IDE.
PIO: PIO, or Programmed Input/Output, is a method of moving data between devices in
a computer, in which all the information must pass through the processor. The ATA/IDE
standard specifies three PIO data transfer rates, namely Mode 0 at 3.3 MBps, Mode
1 at 5.2 MBps, and Mode 3 at 8.3 MBps.
The newer ATA-2 standard specifies two higher data transfer rates—Mode 3
at 11.1 MBps and Mode 4 at 16.6 MBps.
Direct Memory Access: DMA is the ability of an I/O subsystem to transfer data to and
from a memory subsystem without processor intervention.
Ultra ATA/33: Ultra ATA/33 or Ultra DMA/33 is a protocol for transferring data
between a hard disk drive through the system bus to the RAM. The Ultra DMA/33
protocol transfers data in burst mode at a rate of 33.3 MBps, twice as fast as the previous
DMA interface.
Ultra ATA/66: Most of the hard disks available today are ATA/66 complaint. These are
also backward compatible with older PIO and Ultra ATA/33 drives. The requirements for
achieving Ultra ATA/66 performance from these new drives is an ATA/66 capable
motherboard or IDE controller card and an 80-conductor IDE cable instead of the usual
40-pin one. Ultra ATA/66 (also referred to as Ultra DMA/66 or Fast ATA-2) allows for a
maximum burst transfer rate of 66.6 MBps, double the maximum of Ultra ATA/33.
PIO Modes and their specifications
Mode Specification Cycle time (ns) Max. data Cable
transfer rate
(MBps)
PIO Mode 0 ATA 600 3.3 40-way
PIO Mode 1 ATA 383 5.2 40-way
PIO Mode 2 ATA 240 8.3 40-way
PIO Mode 3 ATA-2 180 11.1 40-way
PIO Mode 4 ATA-2 1301 6.6 40-way
Ultra DMA/33 Ultra ATA 60 33 40-way
Ultra DMA/66 Ultra ATA/66 30 66 80-way
SCSI Drives
Pronounced ‘skuzzy’, SCSI stands for Small Computer System Interface. SCSI, like
EIDE, is a bus that controls the flow of data (I/O) between the computer’s processor and
its peripherals, the most common being the hard drive. Unlike EIDE, SCSI requires an
interface or host controller to connect it to a PC’s PCI or ISA bus.
The Small Computer Sysstems Interface (SCSI) drives are independent and thier bus is
far different from others. They do not rely on the BIOS to be able to communicate to the
computer.
When the computer boots, it checks for additional hardware ROMs. As it does this, it
finds your SCSI adapter card, if you have one. It gets no details as to what is attached to
the adapter. As many as 7 SCSI devices can be connected to the adapter. The adapter
watches the flow of data across the SCSI bus. Each device gets its own SCSI address and
can talk with the other SCSI devices across the bus.
The SCSI interface speeds up the computer. There is the original SCSI and and the newer
SCSI -2. When there are two of these in a computer they can really bug you. Proprietary
SCSI standards of many companies may not be able to gel with a SCSI device of a
different brand
SCSI’s most obvious advantage is the number of devices it can control. Whereas
IDE interfaces are restricted to two disk drives, and EIDE interfaces to four devices,
which can include hard disks and CD-ROM drives whereas a SCSI controller can handle
up to 15 devices.
After the first SCSI standard, SCSI01, which was formulated in 1986, the SCSI
interface has evolved to a great extent over the last few years into numerous variations.
The various types differ from each other in several ways, the most important
being cable length limitations and maximum speed.
Fibre Channel: Fibre channel is a high-speed interface designed for multiple disk drive
storage systems. Fibre Channel drives can be installed or removed while the host system
is operational. This interface can provide a maximum bandwidth of 100 MBps and can
support up to 126 devices.
Types of SCSI and their specifications
SCSI version Signalling Bus width Max. data Max. no. of Max. Cable
rate (MHz) (bits) transfer rate devices length (m)
(MBps) supported
SCSI-1 5 8 5 7 6
SCSI-2 5 8 5 7 6
Wide SCSI 5 16 10 15 6
Fast SCSI 10 8 10 7 6
Fast Wide 10 16 20 15 6
SCSI
Ultra SCSI 20 8 20 7 1.5
Ultra SCSI-2 20 16 40 7 12
Ultra2 SCSI 40 16 80 15 12
Ultra 160 80 16 160 15 12
SCSI
Serial ATA: Serial ATA or Serial IDE is all set to replace the parallel IDE interface used
currently. The new standard is a point-to-point protocol that connects each drive directly
to the IDE controller, and will provide a bandwidth of 150 MBps.
To include the content from CRN Book.
Chapter 3 : Choosing the Right Disk
To make a choice between IDE and SCSI, refer following :
Selecting the right drive
Selecting the right hard drive for your system involves two basic principles, which apply
to all other computer components as well-the purpose for which it is required, and the
cost of implementation.
Generally speaking, try to strike a balance between performance, capacity and cost. SCSI
drives are generally much faster than IDE drives, but are also much more expensive in
comparison.
An extra expense involved in SCSI drive is the cost of the SCSI controller card, which
usually has to be bought separately. Though some high-end motherboards do have a
SCSI controller onboard, these motherboards are much more expensive. In case of IDE
drives, the IDE controller is built-in with the motherboard itself.
Performance of a hard disk depends greatly on its rotational speed and the amount of
cache it has. Generally speaking, the faster the rotational speed and greater the cache, the
faster is the speed of the hard disk.
(Diagram)
Pay careful attention to a drive’s specifications to determine the above parameters.
Of course, these specifications also have an effect on the cost of the hard disk.
IDE drives are most suited for desktops and mobile PCs, since it is the least
expensive to implement. Using a SCSI drive in such an environment will not result in a
performance advantage at all. IDE is also a good choice if you don’t need to use more
than four IDE devices together.
SCSI drives are a good choice for high-end servers and in a multi-user
environment where performance is a key issue. You can make full use of SCSI
specifications, and connect as many as 16 devices (including the SCSI controller) on a
single cable.
The Capacity Apt for You
It depends on the environment in which the drive will be used.
* Desktops / Workstation systems: Most of the time, these need 20 Gigabytes to 60
Gigabytes of disc drive storage.
* Servers / Audio-Video / CAD systems: are believed to require 8 Gigabytes to 73
Gigabytes of disc drive storage.
The capacity estimations above can soar depending on the number, size of program
applications installed and the environment related to the system.
Storage Measurement Standards
Discrepancies between the reported and the actual:
Several factors may be considered when you see the reported capacity of a disc drive.
There are two different number systems to express units of storage capacity; binary,
which says that a kilobyte is equal to 1024 bytes, and decimal, which confirms that a
kilobyte is equal to 1000 bytes. The storage industry standard adheres to the decimal
method.
Determine Performance Level
The performance level necessary depends more on how the system is being used:
* Desktop PCs: The average home or small business desktop user is not put to high-level
performance. Hence it is believed that ATA, Performance ATA or SCSI be used for this
category.
* Midrange Servers and Workstations: Midrange servers and workstations designed for
businesss environments with light to medium work loads have, say, approximately 10-50
people accessing the server at a time or workstations on an arbitrary basis during usual
business hours. Performance SCSI is considered best for this usage category.
* High Performance Servers and Workstations: Designed for mission critical, heavy-use
file servers, these could probably stick to the High-End SCSI. Where more than 50
people are at a time accessing workstations and are logged on to servers on a 24-hours-a-
day basis, nothing else could really be better.
Chapter
Installing HDD
Install, Get Set, Go
Hard disk is the beat of your system and its installation can be an interesting challenge.
Here we look at how an IDE hard drive is installed.
Buying a new hard drive is probably the simplest decision one makes when in need of
some big fat space for those gigs of games and mp3’s. Just make a phone call to your
vendor and ask for the biggest, leanest, fastest and cheapest hard drive and that’s just
about it. The real trouble starts when it comes to installing a hard disk.
Unlike PCI cards which can be simply inserted into thier respective slots, one first needs
to make appropriate space for the hard drive, then connect the the IDE and power cable,
make proper jumper settings and finally ascertain that the hard drive is secured firmly in
it’s position and completely immobile. Does it sound too complex?
Read ahead and you shall realize installing a Winchester Drive (popularly known as Hard
Drive) is as simple as replacing a 60 Watt bulb ... well almost!
The Interfaces
Hard Drives are available in two types of interfaces: IDE (Integrated Device
Electronics) / EIDE (Enhanced Integrated Device Electronics) and SCSI (Small
Computer System Interface).
IDE is the defacto standard for all desktop PC’s. Servers and laptops however prefer
SCSI interface as it is more rugged compared to IDE. Due to each of the myraid SCSI
manufacturers having unique techniques of installing, explaining how to install a SCSI
hard disk is beyond the scope of this article.
Do the Groundwork
Over here, we restrict ourselves in explaining how to install an IDE - Hard Drive on a
normal desktop PC. But before that, there are a few absolutely necessary things, which
needs to be considered and understood.
Ground yourself against any static electricity. Touch the metal chasis to discharge any
electric current from your body and then turn off the power supply and remove the plug.
Tie an antistatic wrist-strap before opening the PC to protect against a possible electric
shock.
Most hard drives spin either at 5400rpm or 7200rpm, which is approximately the speed at
which the tyres of an airoplane move when it takes-off making them extremely fragile.
Hard drives do have a plastic protection at the edges, but an occasional drop can render
the drive useless. So be extremely careful in handling the hard drive.
The dorsal side of the hard drive contains some circuitry. Regardless of whether it’s
properly shielded or not, always take care to keep your hard disk on top of a non-
conducting material (magazine, newsapaper) to prevent any short circuit.
Master Hard Drive : A hard drive is said to be “Master” drive if it has been directly
connected to the computer.
Slave Hard Drive : When another hard drive is connected to the drive already connected
directly to the computer, then the former hard drive is said to be Slave while the latter is
Master Drive.
While installing, make sure the jumper settings are correct (i.e. in Master or Slave mode).
If not, the CMOS may display messages such as “Boot Failed” or worse, fail to detect the
hard drive.
On top of every hard drive, there is a small rectangular box, which gives a pictorial
representation explaining the jumper settings to be made when connecting the hard drive
in master or slave mode.
To remove the jumper, make use of a small pointed tool, usually a “pin”, insert it in the
middle of the jumper and slowly remove it. Again be careful as excess amount of force
breaks the jumper pins.
IDE Connector : This is a male connector at the back of the hard drive.An IDE-data
cable is connected to it.Inserting the data cable into the connector can be quite tricky as
both the top and bottom side look quite familiar.So ensure doubly before inserting the
cable.
While remove the IDE cable , adopt a zig-zag manner . Pulling it the way we plug-out
our iron socket can do irreparable damage to the IDE cable . The same applies while
connecting or removing the power chord .
Securing the Drive : After making proper connections & jumper settings , secure the hard
drive in the appropriate sized bay [3-1/2 “ or 5-1/4 ”] Hard drives come in 3-1/2 “ sizes &
thus fit properly in 3-1/2 ” sized bays .
It ay be possible that all 3-1/2 “ bays are pre-occupied . Under Such circumstance ,
make sure you have a mounting breaket & proper screws for the 5-1/4 ” bay .
It is mandatory to secure the hard disk firmly before one starts using . A loose-fit makes
the drive shaky & even a minor jerk , when the drive is in operation will cause irreparable
damage .
Configuration : Once these prerequisite steps are completed , starts the PC . The hard
drive settings now need to be configured in the CMOS . In most cases, the Auto-Detect
option will successfully detect your hard disk . Under rare circumstance, one may need to
specify Cylinders , Sectors , Heads , Write Precomp , Landing Zone , & the Size
manually . These details are normally found on top of the hard disk . If not, check the
accompanying user’s manual .
Figure .
Nowadays, it’s common to find 20 GB & 40 GB sized hard drives . For those who buy
these hard drives with the sole purpose of replacing their 8 GB [ or less ] hard drive
,ensure that your accompanying CMOS supports the capacity of the hard drive you plan
to install .
Some CMOS chips can be made to provide support to the hard drive by
downloading an upgrade from the anufacturers website . If that doesn’t do the tirck , buy
a new CMOS chip [ usually available for less than Rs.400 /- ] but make sure you know
how to install, as it is a grueling task .
Installing a hard disk can at times be tedious. Be extremely careful while handling the
drive as its fragility makes it very susceptible to damage. If it’s the first time you are
doing this, make sure you have some experienced candidate nearby.... Until next time,
happy hard driving.
Steps to Detrmine the Drive Interface
Step 1: Refer to your system documentation on the current drive.
Step 2: Check system properties.
To do this through the Device Manager in Windows 95 / 98:
1. Select Start / Settings / Control Panel.
2. Open the System icon
3. Click Device Manager tab
4. Spread out Disk drives heading
5. Check the phrase GENERIC IDE DISK TYPE. If you find it, your machine supports
IDE drives.
6. If you find the SCSI Controllers heading, your machine may support SCSI hard drives.
Step 3: Check your drive cable and connector.
If a hard drive or CD-ROM is currently installed, your interface can be determined by
checking the drive cable or connector.
ATA: You have an ATA interface drive if your drive connector matches this: 40-pin
connector, 50 mm wide cable.
SCSI: You have a SCSI drive if your drive connector matches one of these:
Narrow SCSI Interface: 50-pin connector, 63 mm wide cable
Wide SCSI Inteface: 68-pin connector, 43 mm wide cable.
Troubleshooting the Disk
There are specifc instances when your hard disk will give you problems. Here’s a peek at
the most common issues that you need to keep an eye on when the hard disk stalls.
When the hard disk drives go on a troubleing spree it really becomes tough to manage the
mess. Sometimes the ultimate option available is formatting the disk and losing all your
data. Here are some common problems and the answers:
The CMOS knows about the Hard Drive, but it still won’t boot, and there are
errors.
The solution: Formatting and partitioning the Hard Drive is required. This should be done
before it is used.
Can the drive be mounted side-ways?
The solution: positively in most of the cases, to mount it upside down, is not agood idea
though. To be sure, write to the company.
How does one add info about a new Hard Drive to the CMOS?
The solution: Usually the F1 or F2 key can be hit during boot up. Some systems allow
you to do it by hitting Ctrl-Alt-Esc,Alt-F2, or Ctrl-S. If not this, then the manual may
work.
The drive will work as a slave, but not as a master, and if as a master not as a slave,
why?
The solution: The settings differ for every drive, and this problem is related to that
particular setting. Check the master/slave jumper on the back of the drive and consult
your manual for correct settings.
The hard drive works fine in one system and then stops working when I upgraded
the motherboard or moved it.
The solution: Double-check all configurations and connections. It could also be an
incompatibility between the two BIOSes and the hard drive. The translation mode affects
how the system reads data off the drive sectors.
Boot from the drive doesn’t work but booting off a system disk does, why?
The solution: This is because formatting and partitioning has not yet happened to your
drive. Maybe a damaged boot sector or possibly a virus. Scan thedrive with a virus
scanner. Check if the primary partition is active so that it is bootable.
Hard Drive gets hot and hotter.
The solution: Hard Drives normally generate a lot of heat. However don’t let them get too
hot to touch - the newer drives especially. A well ventilated case should do the needful.
The Hard Drive just won’t work!
The solution: Check the power connection. The spare power connectors if any, in the
system, might have gone bad. Check all connections and jumpers.
The hard drive won’t boot, or says C: drive failure insert boot disk.
The solution: Check error message on the screen and act accordingly. You may also boot
the system off a floppy or use your disk. If you can read anything off the hard drive then
the drive and controller are fine. Maybe a boot sector is damaged. Recopy
COMMAND.COM, AUTOEXEC.BAT, and CONFIG.SYS, then retest. If error persists,
your drive maybe dead or dying.
The machine doesn’t allow a partition over 2 GB in size.
The solution: If your machine has a FAT16 file system, then this limitation will come
built-in to the operating system. Windows 95 OSR2 and Windows 98 are however
capable of using the FAT32 system, which will get rid of this problem. Else, devide the
drive into partitions where each is less than 2GB.
The Hard Drive seems to have failed.
The solution: This seems to be when the hard drive is not bootable or cannot be detected
by the computer. If it ssis not auto-detectable by the BIOS, it might be a drive failure.
Running a scan disk utility, finds me occasional errors.
The solution: Some files get corrupt during various operations. However, if there are
excessive errors the problem is aggravated. Check for viruses. Ensure the shut down
procedure is followed properly.
You system fails to recognise the large size of your disk
The solution: The BIOS is an old version and cannot recognize a drive a drive larger than
this. An upgradation in the BIOS is required. A driver called dynamic disk can be
installed that servers as a medium between a large disk drive and the old BIOS.
A new hard drive changes all my drive letters.
The solution: Letters are first assigned to the primary partitions, then the logical drive
partitions and later to the other drives. They will change if a primary partition is created
on the new drive. Create only logical partitions on the second drive.
Formatting
fig
The Drive should be formatted and partitioned before using. A necessary step to hard
drive preparation, formatting, cannot be ignored, and most installation cases require a
high level format.
When getting a new drive ready, you will be required to use the FORMAT C: /S
command. This high level command formats the volume Drive C, copies hidden
operating system files to the volume and asks for a label. The bad sectors are marked as
unreadable. This command also overwrites the boot sector and creates the FAT. The root
directory is written and system files are copied.
The second style of formatting is the low-level format and this is already done on your
the drive before you buy.
You would want to low-level format your hard drive when:
* You need to erase all traces of data on the disk.
* Remove corrupted operating systems or viruses.
* Remap the drive to reallocate all bad sectors to other sectors thus replacing bad sectors
with good ones. This is called defect mapping.
Manufacturers recommend you never low-level format at the drive.
HDD: Up close and personal
The hard disk plays a significant role in the functioning of every computer you sell. The
speed at which the PC boots up and the rate at which programs load is directly related to
the hard disk speed. The hard disk’s performance is also critical when the user is
multitasking or processing large amounts of data such as graphics work, editing sound
and video, or working with databases.
A bigger hard disk makes it possible for your customers to store more programs and data.
A faster disk enables them to load software more efficiently. A reliable disk minimizes the
chances of your customer losing data, and your chances of losing a customer.
It is difficult to really understand the factors that affect performance, reliability and
interfacing without knowing how the drive works internally. So let’s take a look at the
components that make up modern hard disk drive, and how they work together to read
and write data.
Chapter
Measure of HDD Performance - 2
Hard sell that hard drive
What are your customers looking for in an HDD ? Find out in this article, so you can give
them what they want, and may be a little extra (disk space, that is)!
When going out to buy a new computer system or when upgrading a computer’s hard
disk drive to one with a larger capacity and better performance, most users try to
anticipate and plan for thier requirements for at least the next two to three years.
According to IBM, market studies show that the typical home computer user consumers
hard drive storage at about a 15 percent compound annual growth rate (CAGR)
