Re: Optimizing Postgresql server and FreeBSD for heavy read and writes

On Thu, Feb 4, 2010 at 3:10 PM, Ivan Voras <ivoras(at)freebsd(dot)org> wrote:

> On 4 February 2010 10:02, Amitabh Kant <amitabhkant(at)gmail(dot)com> wrote:
> > On Wed, Feb 3, 2010 at 10:05 PM, Ivan Voras <ivoras(at)freebsd(dot)org> wrote:
> >>
> >> On 02/03/10 16:10, Amitabh Kant wrote:
> >>>
> >>> Hello
> >>>
> >>> I have a server dedicated for Postgres with the following specs:
> >>>
> >>> RAM 16GB, 146GB SAS (15K) x 4 - RAID 10 with BBU, Dual Xeon E5345 @
> >>> 2.33GHz
> >>> OS: FreeBSD 8.0
> >>
> >> If you really do have "heavy read and write" load on the server, nothing
> >> will save you from the bottleneck of having only 4 drives in the system
> (or
> >> more accurately: adding more memory will help reads but nothing helps
> writes
> >> except more drivers or faster (SSD) drives). If you can, add another 2
> >> drives in RAID 1 and move+symlink the pg_xlog directory to the new
> array.
> >
> > Can't do anything about this server now, but would surely keep in mind
> > before upgrading other servers. Would you recommend the same speed
> > drives(15K SAS) for RAID 1, or would a slower drive also work here (10K
> SAS
> > or even SATA II)?
>
> Again, it depends on your load. It would probably be best if they are
> approximately the same speed; the location of pg_xlog will dictate
> your write (UPDATE / INSERT / CREATE) speed.
>
> Writes to your database go like this: the data is first written to the
> WAL (this is the pg_xlog directory - the transaction log), then it is
> read and written to the "main" database. If the main database is very
> busy reading, transfers from WAL to the database will be slower.
>

Thanks Ivan. I have to go in for upgrade of couple of more servers. I will
be going in for RAID 1 (OS + pg_xlog ) and RAID 10 (Pgsql data), all of them
of same speed.

With regards

Amitabh Kant