Re: Postgresql Performance on an HP DL385 and

Luke,

I'll try it, but you're right, it should not matter. The two systems are:

HP DL385 (dual Opteron 265 I believe) 8GB of RAM, two internal RAID1 U320
10K

Sun W2100z (dual Opteron 245 I believe) 4GB of RAM, 1 U320 10K drive with
LSI MegaRAID 2X 128M driving two external 4-disc arrays U320 10K drives in a
RAID10 configuration. Running same version of LInux (Centos 4.3 ) and same
kernel version. No changes within the kernel for each of them. Running the
same *.conf files for Postgresql 7.4.13.

Steve

On 8/18/06, Luke Lonergan <llonergan(at)greenplum(dot)com> wrote:
>
> Steve,
>
> One thing here is that "wal_sync_method" should be set to "fdatasync" and
> not "fsync". In fact, the default is fdatasync, but because you have
> uncommented the standard line in the file, it is changed to "fsync", 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, I'm 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
>
>
>
>
>
>
>