Re: Postgresql Performance on an HP DL385 and

Steve,

One thing here is that ³wal_sync_method² should be set to ³fdatasync² and
not ³fsync². In fact, the default is fdatasync, but because you have
uncommented the standard line in the file, it is changed to ³fsync², which
is a lot slower. This is a bug in the file defaults.

That could speed things up quite a bit on the xlog.

WRT the difference between the two systems, I¹m kind of stumped.

- Luke

On 8/18/06 12:00 PM, "Steve Poe" <steve(dot)poe(at)gmail(dot)com> wrote:

>
> Luke,
>
>> ISTM that the main performance issue for xlog is going to be the rate at
>> which fdatasync operations complete, and the stripe size shouldn't hurt
>> that.
>
> I thought so. However, I've also tried running the PGDATA off of the RAID1 as
> a test and it is poor.
>
>
>
>> What are your postgresql.conf settings for the xlog: how many logfiles,
>> sync_method, etc?
>
> wal_sync_method = fsync # the default varies across platforms:
> # fsync, fdatasync, open_sync, or
> open_datasync
> # - Checkpoints -
>
> checkpoint_segments = 14 # in logfile segments, min 1, 16MB each
> checkpoint_timeout = 300 # range 30-3600, in seconds
> #checkpoint_warning = 30 # 0 is off, in seconds
> #commit_delay = 0 # range 0-100000, in microseconds
> #commit_siblings = 5
>
> What stumps me is I use the same settings on a Sun box (dual Opteron 4GB w/
> LSI MegaRAID 128M) with the same data. This is on pg 7.4.13.
>
>
>
>>> > The 6-disc RAID10 you speak of is on the SmartArray 642 RAID adapter.
>>
>> Interesting - the seek rate is very good for two drives, are they 15K RPM?
>
> Nope. 10K. RPM.
>
>
> HP's recommendation for testing is to connect the RAID1 to the second channel
> off of the SmartArray 642 adapter since they use the same driver, and,
> according to HP, I should not have to rebuilt the RAID1.
>
> I have to send the new server to the hospital next week, so I have very little
> testing time left.
>
> Steve
>
>
>
>
>