The hard disk drive in your system is the "data center" of the
PC. It is here that all of your programs and data are stored
between the occasions that you use the computer. Your hard disk (or
disks) are the most important of the various types of permanent
storage used in PCs (the others being floppy disks and other
storage media such as CD-ROMs, tapes, removable drives, etc.) The
hard disk differs from the others primarily in three ways: size
(usually larger), speed (usually faster) and permanence (usually
fixed in the PC and not removable).
Hard disk drives are almost as amazing as microprocessors in
terms of the technology they use and how much progress they have
made in terms of capacity, speed, and price in the last 20 years.
The first PC hard disks had a capacity of 10 megabytes and a cost
of over $100 per MB. Modern hard disks have capacities approaching
100 gigabytes and a cost of less than 1 cent per MB! This
represents an improvement of 1,000,000% in just under 20 years, or
around 67% cumulative improvement per year. At the same
time, the speed of the hard disk and its interfaces have increased
dramatically as well.
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Top view of a 36 GB, 10,000 RPM, IBM SCSI
server hard disk, with its top cover removed.
Note the height of the drive and the 10 stacked platters.
(The IBM Ultrastar 36ZX.)
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Original image © IBM Corporation
Image used with permission.
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Your hard disk plays a significant role in the following
important aspects of your computer system:
- Performance: The hard disk plays a very important role
in overall system performance, probably more than most people
recognize (though that is changing now as hard drives get more of
the attention they deserve). The speed at which the PC boots up and
programs load is directly related to hard disk speed. The hard
disk's performance is also critical when multitasking is being used
or when processing large amounts of data such as graphics work,
editing sound and video, or working with databases.
- Storage Capacity: This is kind of obvious, but a bigger
hard disk lets you store more programs and data.
- Software Support: Newer software needs more space and
faster hard disks to load it efficiently. It's easy to remember
when 1 GB was a lot of disk space; heck, it's even easy to remember
when 100 MB was a lot of disk space! Now a PC with even 1 GB is
considered by many to be "crippled", since it can barely hold
modern (inflated) operating system files and a complement of
standard business software.
- Reliability: One way to assess the importance of an item
of hardware is to consider how much grief is caused if it fails. By
this standard, the hard disk is the most important component by a
long shot. As I often say, hardware can be replaced, but data
cannot. A good quality hard disk, combined with smart maintenance
and backup habits, can help ensure that the nightmare of data loss
doesn't become part of your life.
This chapter takes a very detailed look at hard disks and how
they work. This includes a full dissection of the internal
components in the drive, a look at how data is formatted and
stored, a discussion of performance issues, and a full analysis of
the two main interfaces used to connect hard disks to the rest of
the PC. A discussion is also included about the many confusing
issues regarding hard disks and BIOS versions, and support for the
newer and larger hard disks currently on the market. Finally, a
full description is given of logical hard disk structures and the
functioning of the FAT and NTFS file systems, by far the most
popular currently used by PCs.
Next: A Brief History of the Hard
Disk Drive
