In the last episode (Mar 20), Poul-Henning Kamp said:
> In message <[EMAIL PROTECTED]>, Alfred Perlstein writes:
> >* Poul-Henning Kamp <[EMAIL PROTECTED]> [000320 11:45] wrote:
> >>
> >> Before we redesign the clustering, I would like to know if we
> >> actually have any recent benchmarks which prove that clustering is
> >> overall beneficial ?
> >
> >Yes it is really benificial.
>
> I would like to see some numbers if you have them.
For hardware RAID arrays that support it, if you can get the system to
issue writes that are larger than the entire RAID-5 stripe size, your
immensely slow "read parity/recalc parity/write parity/write data"
operations turn into "recalc parity for entire stripe/write entire
stripe". RAID-5 magically achieves RAID-0 write speeds! Given 32k
granularity, and 8 disks per RAID group, you'll need a write
size of 32*7 = 224k. Given 64K granularity and 27 disks, that's 1.6MB.
I have seen the jump in write throughput as I tuned an Oracle
database's parameters on both Solaris and DEC Unix boxes. Get Oracle
to write blocks larger than a RAID-5 stripe, and it flies.
--
Dan Nelson
[EMAIL PROTECTED]
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