Raidtest/3Ware 6000 Throughput

Chuck Swiger cswiger at
Thu Mar 16 19:08:18 UTC 2006

Don O'Neil wrote:
> I would have thought I would at least see the raw single drive throughput,
> plus maybe a bit more.

When choosing RAID levels, you are making a tradeoff between performance,
reliability, and cost.  Choosing RAID-5 means you value performance the least of
the three:

If you prefer...             ...consider using:
performance, reliability:    RAID-1 mirroring
performance, cost:           RAID-0 striping
reliability, performance:    RAID-1 mirroring (+ hot spare, if possible)
reliability, cost:           RAID-5 (+ hot spare)
cost, reliability:           RAID-5
cost, performance:           RAID-0 striping

If you've got enough drives, using RAID-10 or RAID-50 will also improve
performance compared to stock RAID-1 or RAID-5 modes.

> I've benched these drives independantly at 20+
> MB/second... Is the 3ware card really slowing things down that much with the
> RAID-5 overhead?

Yes.  It will be less noticeable with big transactions, and more noticeable with
lots of tiny ones.

> What "real HW RAID-5" controller would you suggest? I'd like to stick with
> IDE/ATA since I have a bunch of drives already.

Maybe the 3ware 9500S -4 or -8...?

> Am I maybe CPU bound, or have another issue? 

You're probably I/O bound, not CPU bound.


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