Re: SCSI vs SATA

On Thu, 5 Apr 2007, Scott Marlowe wrote:

>> I've read some recent contrary advice. Specifically advising the
>> sharing of all files (pg_xlogs, indices, etc..) on a huge raid array
>> and letting the drives load balance by brute force.
>
> The other, at first almost counter-intuitive result was that putting
> pg_xlog on a different partition on the same array (i.e. one big
> physical partition broken up into multiple logical ones) because the OS
> overhead of writing all the data to one file system caused performance
> issues. Can't remember who reported the performance increase of the top
> of my head.

I noticed this behavior on the last Areca based 8 disk Raptor system I built.
Putting pg_xlog on a separate partition on the same logical volume was faster
than putting it on the large volume. It was also faster to have 8xRAID10 for
OS+data+pg_xlog vs 6xRAID10 for data and 2xRAID1 for pg_xlog+OS. Your
workload may vary, but it's definitely worth testing. The system in question
had 1GB BBU.

--
Jeff Frost, Owner <jeff(at)frostconsultingllc(dot)com>
Frost Consulting, LLC http://www.frostconsultingllc.com/
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