Drive comparison chart

Goto this page:
http://www.storagereview.com/comparison.html

Select SR File Server Drivemark 2002

You get a graph of all the disc drives ( including scsi and serial ata ( sata ) ) showing what the number of operations per second a drive is capable of performing.

Hard drive speed is complex and dependant on a number of factors - not just the headline quoted MB/s transfer rate.
The headline datarate is misleading.

Disc drives are not created equal.

Drives also have rotational latency and seek time issues which are much more important.
The rotational latency is because the drive is continuously rotating, and it takes a certain amount of time for the platter to move under the read heads.
This speed is related to the rpm of the drive.

The number of IOs/second:

Imagine you have a large database say many megabytes, ( just like a movie file )

What these values tell you is the number of RANDOM reads within that file that can be done per second.

Standard ata drives, only manage around 100 random reads per second.

So your fast computer is stalled by the speed of your disc drive - if you are doing things like serving lots of webpages - to lots of different users - who all need access to different pages.

This is similiar to the way catalyst works.