On Monday, 20 March 2000 at 15:23:31 -0600, Dan Nelson wrote:
> 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.
Agreed. This is on the Vinum wishlist, but it comes at the expense of
reliability (how long do you wait to cluster? What happens if the
system fails in between?). In addition, for Vinum it needs to be done
before entering the hardware driver.
Greg
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