Craig A. James wrote:
I'm experiment with RAID, looking for an inexpensive way to boost performance. I bought 4 Seagate 7200.9 120 GB SATA drives and two SIIG dual-port SATA cards. (NB: I don't plan to run RAID 0 in production, probably RAID 10, so no need to comment on the failure rate of RAID 0.)

I used this raw serial-speed test:

  time sh -c "dd if=/dev/zero of=./bigfile bs=8k count=1000000 && sync"
  (unmount/remount)
  time sh -c "dd if=./bigfile of=/dev/null bs=8k count=1000000 && sync"

Which showed that the RAID 0 4-disk array was almost exactly twice as fast as each disk individually. I expected 4X performance for a 4-disk RAID 0. My suspicion is that each of these budget SATA cards is

I am assuming linux here, Linux software raid 0 is known not to be super duper.

Secondly remember that there is overhead involved with using raid. The direct correlation doesn't work.

Joshua D. Drake




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