Hard Drive Advancements

In 1957, Cyril Northcote Parkinson published 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 hard disk drive more than 20 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 10 megabyte, not gigabyte) Miniscribe model 2012, which was a 5 1/4" (platter) drive that was 203.2mmx146mmx82.6mm or 8"x5.75"x3.25" in overall size and weighed 2.5kg (5.5 lb., which is heavier than some of today's laptop computers)! By comparison, one of the biggest drives available to datethe Hitachi 7K500 SATA driveuses smaller 3 1/2" platters, is about 5 3/4"x4"x1" (146mmx102mmx25mm) in overall size, weighs only 1.54 lb. (0.70kg), and stores a whopping 500GB (which is 50,000 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 transfer the data to and from the disk quickly. 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, most commonly used drives feature the Serial ATA interface, which offers variable media data transfer rates of up to 66MBps (average rates are lower, up to about 50MBps). Much like the increase in drive capacity, the speed of the interface has also come a long way since the MFM and RLL interfaces that were commonplace in the '80s. As always, the interfaces are much faster than the actual drives. The Parallel ATA, Serial ATA, and SCSI interfaces are commonplace now and offer data transfer rates of up to 133MBps for Parallel ATA, 150 and 300MBps for Serial ATA, and 320MBps bandwidth for Ultra-320 SCSI. All these interfaces are much faster than the drives they support, meaning that the true transfer rate you will see is almost entirely limited by the drive and not the interface you choose. The modern interfaces have bandwidth to spare for future developments and advances in hard disk technology.

To give you an idea of how far hard drives have come in the 20+ years they have been used in PCs, I've outlined some of the more profound changes in PC hard disk storage:

• Maximum storage capacities have increased from the 5MB and 10MB 5 1/4" full-height drives available in 1982 to 500GB in 2005 for 3 1/2" half-height drives (Hitachi 7K500, 500GB SATA), 160GB for notebook system 2 1/2" drives (Seagate Momentus 5400.3 160), and 60GB for 1 4/5" drives (Toshiba MK-6006GAH, 60GB). Hard drives smaller than 40GB 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 50MBps for some of the fastest drives today (Western Digital Raptor WD74GD) or more than 80MBps for the fastest SCSI drive (Seagate Cheetah 15K.4).

• 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 3.3ms for some of the fastest drives today (Seagate Cheetah 15K.4).

• In 1982 and 1983, a 10MB drive and controller cost more than $2,000 ($200 per megabyte), which would be more than double that in today's dollars. Currently, the cost of desktop hard drives (with integrated controllers) has dropped to 0.03 cents per megabyte or lessor about 300GB for $100! Laptop drives have fallen to 0.1 cents per megabyte or less, or about 100GB for $100.