Re: IOPS from RAID units
- From: Cydrome Leader <presence@xxxxxxxxxxxxxx>
- Date: Fri, 21 Mar 2008 16:15:58 +0000 (UTC)
davidhoffer <comp.arch.storage-forum@xxxxxxxxxxxxxxxxx> wrote: > > The
IOPS the array can deliver is the aggregate of all the drives in the raid
group less the hot spares and parity drives. Its more complicated than
that of course but its a not bad rule of thumb. So 10 data drives that can
each deliver 100 iops could (in theory) deliver 1000 iops when bound
this is a bad assumption.
let me ruin this example.
I write 5 bytes to a raid5 array of 10 drives.
that's one operation to the host.
it's also at least 10 reads and 10 writes if you're using 10 drives, and
probably more depending on the stripe size of the raid array.
we're looking at negative performance gains here in addition to an
incredible increase of operations inside that raid group.
together into a raid group. If you want to know what performance you will
get out of a SPECIFIC array with SPECIFIC applications, that can be
calculated more accurately....at great expense of course. > >
calculating performance is just stupid. Run benchmarks and see what really
happens as that's what counts.
.
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