On Thu, Feb 4, 2010 at 3:10 PM, Ivan Voras <ivo...@freebsd.org> wrote:
> On 4 February 2010 10:02, Amitabh Kant <amitabhk...@gmail.com> wrote: > > On Wed, Feb 3, 2010 at 10:05 PM, Ivan Voras <ivo...@freebsd.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
