1. Hard Disk Storage

2. Definition of a Hard Disk
The hard disk drive (HDD) is one of the most important and yet mysterious parts of a computer system.
HDDs are sealed units used for nonvolatile data storage.
Nonvolatile, or semipermanent, storage means that the storage device retains the data even when no power is supplied to the computer.
Hard disk drives contain rigid, disk-shaped platters, usually constructed of aluminum or glass.
Unlike floppy disks, the platters can’t bend or flex—hence the term hard disk.
In most drives you can’t remove the platters, which is why they are sometimes called fixed disk drives.

3. Definition of a Hard Disk
Hard disk drives are sometimes referred to as Winchester drives.
This term dates back to 1973, when IBM introduced the model drive, which had 30MB of fixed platter and 30MB of removable platter storage on separate spindles.
The drive was codenamed Winchester by project leader Ken Haughton because the original capacity designation (30-30) sounded like the popular (caliber-grains of charge) cartridge used by the Winchester 94 rifle introduced in 1895.
The original 3340 “Winchester” drive was the first to use a sealed head/disk assembly, and the name has since been applied to all subsequent drives with similar technology

4. Hard Drive Advancements
The first hard drive appeared in 1956.
Before (1983)
10MB Miniscribe model 2012
5 1/4" (platter) drive
8"×5.75"×3.25“
2.5kg (5.5lb.) (weight of a laptop today)
Now
1.5TB 3 1/2" drive
5 3/4"×4"×1“
1.54 lb. (0.70kg)
150,000 times more storage in a package that is about one-sixth the size and one-fourth the weight

5. Hard Drive Advancements
In 2006, the hard disk drive celebrated its 50th anniversary, a milestone in computing technology. By the time PCs arrived on the scene in 1981, hard drives of 5MB in capacity were available.
To give you an idea of how far hard drives have come in the 25+ years they have been used in PCs, I’ve outlined some of the more profound changes in PC-based hard disk storage:
Maximum storage capacities have increased from the 5MB 5 1/4" full-height drives available in 1981 to 1.5TB in 2008 for 3 1/2" half-height drives, 500GB for laptop 2 1/2" drives, and 250GB for 1.8" drives. Hard drives smaller than 80GB are rare in new desktop or even laptop systems.

6. Hard Drive Advancements
Data transfer rates to and from the media (sustained transfer rates) have increased from about 100KBps for the original IBM XT in to an average of over 100MBps for some of the fastest drives today, or more than 130MBps average for the fastest SAS (Serial Attached SCSI) drives.
Average seek times (how long it takes to move the heads to a particular cylinder) have decreased from more than 85ms (milliseconds) for the 10MB drives IBM used in the 1983 vintage PC- XT to as low as 3.3ms for 15,000 rpm drives today.
In 1982 a 10MB drive and controller cost more than $2,000 ($200,000 per gigabyte), a figure which would actually be more than double that amount in today’s dollars. Currently, the cost of desktop hard drives (with integrated controllers) has dropped to $0.09 per gigabyte or less— or about 1,000GB for $90! Laptop drives have fallen to $0.18 per gigabyte or less, or about 500GB for $90.

7. Hard Drive Advancements
IBM sold its Hard Disk Drive operations division to Hitachi on January 6, 2003.
The resulting new company, called Hitachi Global Storage Technologies ( comprises the hard disk drive operations of Hitachi and IBM and is headquartered in San Jose, California.
Hitachi Global Storage Technologies now manufactures, sells, and supports the former IBM Travelstar, Microdrive, Ultrastar, and Deskstar product lines.
The new company is 70% owned by Hitachi, with the remaining shares held by IBM. Hitachi assumed full ownership at the end of 2005, and IBM has no involvement in the management of the new company.
IBM invented the hard drive, so it is sad to see the company exit the business.

8. Form Factors
The cornerstone of the PC industry has always been standardization.
With disk drives, this is evident in the physical and electrical form factors that comprise modern drives.
By using industry-standard form factors, you can purchase a system or chassis from one manufacturer and yet physically and electrically install a drive from a different manufacturer.
Form factor standards ensure that available drives will fit in the bay, the screw holes will line up, and the standard cables and connections will plug in.
Without these industry standards, there would be no compatibility between different chassis, motherboards, cables, and drives

9. Form Factors
Currently, 3 1/2" drives are the most popular for desktops, whereas 2 1/2" and smaller drives are popular in laptops and other portable devices.
Parallel ATA drives have been replaced by Serial ATA drives in new systems.
Parallel ATA drives will still be available for upgrading older systems, although the choices are becoming more limited.

10. 5 1/4" Drive
Shugart Associates first introduced the 5 1/4" form factor along with the first 5 1/4" floppy drive in 1976.
The story goes that founder Al Shugart then left that company and founded Seagate Technologies, which introduced the first 5 1/4" (Model ST-506, 5MB capacity) hard disk in 1980, predating the IBM PC.
IBM later used the Seagate ST-412 (10MB) drive in some of its PC- XT models, which were among the first PCs to be sold with hard drives built in.
The 5 1/4" half-height form factor is still used as the form factor for optical drives and is the standard form factor for larger drive bays in all modern desktop PC chassis.

11. 3 1/2" Drive
Sony introduced the first 3 1/2" floppy drive in 1981, which used a smaller width and depth but the same height as the half-height 5 1/4" form factor.
These were called 3 1/2" half-height drives, even though there was no such thing as a “full-height” 3 1/2" drive.
Rodime followed with the first 3 1/2“ half-height hard disk in
Later 3 1/2" floppy and hard drives would be reduced in height to only 1", which was just under one-third of the original 5 1/4" full- height form factor (these were sometimes called 1/3-height drives).
Today, the 1" high version has become the modern industry- standard 3 1/2“ form factor.

12. 2 1/2" Drive
PrairieTek introduced the 2 1/2" form factor in 1988, which proved to be ideal for laptop and notebook computers. As laptop sales grew, so did sales of the 2 1/2" drives.
Although PrairieTek was the first with that form factor, other drive manufacturers quickly capitalized on the market by also introducing 2 1/2" drives.
Finally, in 1994 Conner Peripherals, Inc., paid $18 million for PrairieTek’s 2 1/2“ disk drive technology and PrairieTek went out of business.
Since the 2 1/2" drives first appeared, virtually all laptop and notebook systems have used them.
Although 2 1/2" drives can also be used in desktop systems, the 3 1/2" drive continues to dominate the desktop market due to greater capacity and speed and lower cost.

13. 2 1/2" Drive
The 2 1/2" drives have been manufactured in various thicknesses (or heights), and many notebook or laptop systems are restricted as to how thick a drive they can support.
Here are the common thicknesses that have been available:
■ 8.5mm ■ 9.5mm ■ 12.5mm
■ 12.7mm ■ 17.0mm ■ 19.0mm
The most popular sizes have been the 9.5mm and 12.5mm thick versions, with almost all modern systems using the 9.5mm form factor.
A thinner drive can almost always be installed in place of a thicker one; however, most systems do not have the room to accept a thicker drive than they were originally designed to use.

14. 1.8" Drive
The 1.8" drive was first introduced by Integral Peripherals in and has had problems gaining acceptance in the marketplace ever since.
This size was initially created because it fit perfectly in the PC Card (PCMCIA) form factor, making it ideal as add-on removable storage for laptop and notebook systems.
Unfortunately, the 1.8" drive market was slow to take shape, and in 1998 an investment group called Mobile Storage bought Integral Peripherals’ 1.8" drive technology for $5.5 million; Integral Peripherals then went out of business.
Several other companies have introduced 1.8" drives over the years—most notably HP, Calluna, Toshiba, and Hitachi.

15. 1.8" Drive
Of those, only Toshiba and Hitachi continue to manufacture drives in that format. HP exited the disk drive market completely in 1996, and Calluna finally ceased operation in 2001.
Toshiba introduced its 1.8" drives (available in the physical format of a Type II PC Card) in 2000, and Hitachi entered the 1.8" drive market in 2003.
The 1.8“ drives are available in capacities of up to 250GB or more.
Note: HP introduced a 20MB 1.3" disk drive called the KittyHawk in 1992, originally intended for the handheld computer market. In 1994, HP followed with a 40MB model. These small drives were expensive and proved to be too far ahead of their time, as were the handheld computers they were intended for. After 2 years of low sales, HP discontinued the KittyHawk family.

16. 1" Drives
During 1998, IBM introduced a 1" drive called the Microdrive, incorporating a single platter about the size of a quarter!
Current versions of the Microdrive can store up to 8GB or more.
These drives are available with several interfaces including that of a Type II Compact Flash (CF) card, which means they can be used in almost any device that takes CF cards, including digital cameras, personal digital assistants (PDAs), and MP3 players.
In 2004, Toshiba introduced the smallest drive to date: the 0.85" drive, which is about the size of a postage stamp and stores up to 4GB.
This drive is designed for use in cell phones, digital audio players, PDAs, digital still cameras, camcorders, and more.