Hardware Reference
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his famous compilation of essays titled Parkinson's Law , which begins with the statement, “Work
expands so as to fill the time available for its completion.” A corollary of Parkinson's most famous
“law” can be applied to hard drives: “Data expands so as to fill the space available for its storage.”
This, of course, means that no matter how big a drive you get, you will find a way to fill it. I know that
I have lived by that dictum since purchasing my first HDD nearly 30 years ago.
Even though I am well aware of the exponential growth of everything associated with computers, I am
still amazed at how large and fast modern drives have become. The first hard drive I purchased in
1983 was a 10MB (that's megabyte, not gigabyte) Miniscribe model 2012, which was a 5 1/4-inch
(platter) drive that was 203.2mm×146mm×82.6mm or 8 inches×5.75 inches×3.25 inches in overall
size and weighed 2.5kg (5.5 lb., which is heavier than many laptop computers)! By comparison, a
modern 4TB 3 1/2-inch drive is about 5 3/4 inches×4 inches×1 inch (146mm×102mm×25mm) in
overall size, weighs only 1.54 lb. (0.70kg), offering 400,000 times more storage in a package that is
about one-sixth the size and one-fourth the weight of my old Miniscribe.
Obviously, the large storage capacities found on modern drives are useless unless you can also
quickly transfer the data to and from the disk. The hard disk as found in the original IBM XT in 1983
had a constant data transfer rate from the media of about 100KBps. Today, hard disk drives feature
average transfer rates of up to 150MBps or more, while solid-state drives have even faster transfer
rates of 550MBps or more. That's from 1,000 to 5,500 times faster!
Much like the increases in drive capacity and performance, the speed of the interface has come a long
way since the ST-506/412 interface used in the original IBM-PC and XT, which had a transfer rate of
only 5Mbps. Modern interfaces offer data transfer rates of up to 133MBps for Parallel AT
Attachment (ATA), up to 600MBps for Serial ATA (SATA) and Serial Attached SCSI (SAS), and up
to nearly 2,000MBps for SATA Express. Up until the advent of high-performance Solid-State Drives
(SSDs), these interfaces were typically much faster than the individual drives they supported,
meaning that the true transfer rate you will see was almost entirely limited by the drive and not the
interface you choose. SSDs have changed that game and have been pushing the industry to develop
faster interfaces. The modern interfaces have bandwidth to spare for future developments and
advances in hard disk technology.
Note
The topic Parkinson's Law (ISBN: 1-56849-015-1) is still in print and is, in fact, considered
one of the essential tomes of business and management study even today.
In 2006, the HDD 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 30+ years they have been used in PCs, I outlined some
of the more profound changes in PC-based hard disk storage:
• Maximum storage capacities have increased from the 5MB 5 1/4-inch full-height drives
available in 1981 to 4TB in 2012 for 3 1/2-inch half-height drives, 1.5TB for laptop 2 1/2-inch
drives, and 250GB for 1.8-inch drives. Hard drives smaller than 200GB are rare in new
desktop or even laptop systems.
• Data transfer rates to and from the media (sustained transfer rates) have increased from about
100KBps for the original IBM XT in 1983 to an average of over 150MBps for some of the
 
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