HD Buffer sizes and rpm - effect on performance?

[johnw]

Can someone please explain the difference in hard drive performance between a 2 MB buffer (is this the default buffer size?) and an 8 MB buffer?

Also, seems that I read somewhere that there is very little to be gained by going to a 7200 rpm unit from a 5200 rpm unit; the source I saw said that the normal average access time for a 5200 rpm unit is about 9 ms and for a 7200 rpm unit it goes down only to 8 ms. But how does buffer size factor into this? Thanks for the info.

I'm still learnin'.

[saphalline]

Today's ATA/100 and ATA/133 hard drives do indeed have a default buffer size of 2MB. Back in the day of ATA/33 and ATA/66 hard drives, 512KB was the default buffer size, with 1MB and 2MB drives being much more expensive. My how far we've come in just two years! :D

8MB buffer hard drives are rare in the ATA arena, with one of the notable exceptions being the Western Digital "Special Edition" HD's, denoted by the "JB" instead of "BB" on the model description (as in the WD800JB vs WD800BB - both 80GB). Yes, these WD Special Editions really do burn up the hard drive market with their performance, but spindle speed (rpm's) also matters.

Standard spindle speed these days is 7200rpm, anything slower is well... slower! 5400rpm fails to please these days, as hard drive throughput (data transfer speed in MB per second) goes far beyond the access time. 9ms vs 8ms is no big deal, true, but that's just the latency for immediately finding the right spot on the disks. After that, spindle speed, areal density, ATA max throughput, buffer size, drive electronics, and many other factors contribute to a fast hard drive. Suffice to say that slower hard drives receive fewer of these speed enhancements and have, for the most part, been driven out of existence by the cheap cost of producing high-quality 7200rpm hard drives.

Even if your motherboard can only handle ATA/66, it just doens't make sense to buy anything slower than a cheap ATA/100 or ATA/133 hard drive with a 2MB buffer, 7200rpm spindle speed, and 8ms access time. Drives such as these with 20-40GB of space sell for less than $90 these days, and are fully compatible with all ATA speeds, from /33 to /133.