Old article I know but still a great resource for people looking at power consumption and speed differences. Wanted to help people understand hard drive performance a bit.
Hard drive performance isn't a flat number. It falls into overlapping categories of read, write, random (bits of information in different places) and sequential (large blocks of information in one spot, then move on)
Drive performance factors are seek time and data rate.
More data density on the same spin speed (i.e. bigger drive, 100GB vs 250GB) means the data rate goes up. That is why a 5400rpm drive with a high data density can "beat" a 7200rpm drive with a lower one. HOWEVER, that only effects SEQUENTIAL read and write.
To increase random read/write performance, you increase the RPM of the drive. This is because in random read/write, the drive spends more of its time seeking new locations than doing things at those locations. (11ms to seek, 1ms or less to write... big ratio!)
90% of the time, when you care about drive performance, you will be experiencing RANDOM read and write. The reason for this is that most things fall into these random read/write performance buckets:
* reading from one file, processing, and writing to another. (like copying files)
* reading from multiple small files
* searching through one large file, reading bits of it at a time.
You experience sequential read/write performance under the following situations:
* Copying large files from one DEFRAGGED disk onto another defragged disk
* Creating a large amount of information using a small amount of information or information that is not stored on the disk (converting compressed video to uncompressed, rendering video from a small scene file, recording your screen to disk, recording video or audio.)
* Streaming something from the disk for display.
Note that some of those situations will not necessarily run faster with a faster disk. Can't record video or audio faster than it is coming into your camera or mic. ; ) Large file copies are a bigger deal but I don't frequently copy more than 2-3 gigs at a time. So a 5400 disk with high data density can win benchmarks, but it will lose in RL use most of the time because sequential performance is actually quite difficult to get in RL.