Just a random tidbit I thought I would post. I have a server at home acting as an iSCSI SAN. I ran a batch of hdparm tests against it, a single SATA drive in that array, a 5 disc SAS array in a compaq server and a 4 disc RAID 5 3Ware SATA array. here are the results. These are averages ran over 5 passes BTW on an otherwise silent machine. The CPU’s are all different speeds, but are all of the same class (dual core 800mhz FSB)
5 disc SAS array with 136g 10k drives
Timing cached reads: 13336 MB in 2.00 seconds = 6673.96 MB/sec
Timing buffered disk reads: 98 MB in 1.18 seconds = 83.31 MB/sec
4 disc Linux RAID 5 with 3Ware 9650SE and 500g 7200RPM drives
Timing cached reads: 6576 MB in 2.00 seconds = 3293.08 MB/sec
Timing buffered disk reads: 448 MB in 3.00 seconds = 149.20 MB/sec
Single 500g 7200 RPM SATA drive
Timing cached reads: 14220 MB in 2.00 seconds = 7119.78 MB/sec
Timing buffered disk reads: 198 MB in 3.02 seconds = 65.51 MB/sec
6 500g 7200 RPM SATA drives in a software RAID 5 array
Timing cached reads: 14364 MB in 2.00 seconds = 7191.86 MB/sec
Timing buffered disk reads: 852 MB in 3.00 seconds = 283.64 MB/sec
Now, for those of you that have storage experience, yes I didn’t mention chunk size or any of that fun stuff. But the point that I’m trying to get across is that, if you have the CPU cycles to spare, software RAID can be wicked fast.