There was a time when the performance of hard disks was one of the most underrated
aspects of overall system performance. Hard disks were considered only "a place to
keep stuff" and little heed given to how they affected the operation of the PC as a
whole. Over the last few years this has changed dramatically, and hard disk performance
issues are now getting the attention they deserve. The problem with hard disk performance
however is that it is not easy to understand. There are many different issues in how
performance is assessed and measured. There are interactions between components with which
anyone seeking to really grasp hard disk performance must contend. And the technology
changes so rapidly that what is the "fastest" today will probably be
"second best" within a few months--or even weeks in many cases!
The purpose of this section is to take a detailed look at all the facets of hard disk
performance. I start by discussing various issues in how performance is evaluated and
measured. Then, I cover in full detail the common hard disk performance specifications and
also the internal and external factors that affect performance.
In order to avoid some confusion, let me try to explain the difference between
"performance specifications" and "performance factors", at least as I
see them. A performance specification is a figure provided by a manufacturer that
attempts to express an element of the drive's performance relative to other drives on the
market. A performance factor is something about the drive (internal factor) or
its environment (external factor) that affects the performance of the drive. Clearly,
these are interrelated; factors affect specifications, and specifications indicate the
impact of various factors. I considered putting them all together, but this would be
confusing, since some specifications sort of "stand alone" while others are
derived from one or several performance factors. Also, some specifications are a result of
various factors. To be honest, this was one of the most difficult areas of the site to
organize.
Before even delving into this section, it's important to remember that performance
always comes at a price. As with most things, there are tradeoffs involved. If performance
is your chief goal in a storage system you can have it, but you will either pay for it, or
give up something else in exchange (capacity, flexibility, simplicity, etc.) There are no
free lunches, although the general increase in performance of all hard disks
means that even inexpensive drives today perform very well compared to their predecessors.
Next: Hard Disk
General Performance Issues
