>>>>> "Brad" == Brad Knowles <email@example.com> writes:
Brad> At 10:02 AM -0500 1999/12/17, David Gilbert wrote:
>> Well... it's RAID-5 across the same 8 drives with all 8 drives on
>> one LVD chain (same configuration as the other test). I have tried
>> the 128k stripe, but it was slower than the default 64k stripe.
Brad> One of the lessons I learned from Greg was that, when dealing
Brad> with RAID implementations in hardware, you should usually take
Brad> their "native" stripe size, since that's the one that will
Brad> usually perform best.
Brad> It's only when you do software RAID (e.g., vinum) that you can
Brad> choose larger or smaller stripe sizes with a reasonable
Brad> expectation that you will get the particular performance
Brad> enhancement that you're hoping for.
Another thing that I find very different betweent he vinum software
RAID-5 and the hardware I've tried (I've used both the DPT and the
MegaRAID controllers) that the latency of a command can be incredible
on the hardware raid. If you type (for instance) 'du -ks foo' where
foo is a big directory on the hardware raid, and then press CTRL-C, it
can take 10 to 15 seconds to come back (I'm assuming that this is
queued I/O requests).
|David Gilbert, Velocet Communications. | Two things can only be |
|Mail: firstname.lastname@example.org | equal if and only if they |
|http://www.velocet.net/~dgilbert | are precisely opposite. |
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