Re: hardware performance and some more

On 24 Jul 2003 at 15:54, Kasim Oztoprak wrote:

> The questions for this explanation are:
> 1 - Can we use postgresql within clustered environment?
> 2 - if the answer is yes, in which method can we use postgresql within a cluster?
> active - passive or active - active?

Coupled with linux-HA( See http://linux-ha.org) heartbeat service, it *should*
be possible to run postgresql in active-passive clustering.

If postgresql supported read-only database so that several nodes could read off
a single disk but only one could update that, a sort of active-active should be
possible as well. But postgresql can not have a read only database. That would
be a handy addition in such cases..

> Now, the second question is related to the performance of the database. Assuming we have a
> dell's poweredge 6650 with 4 x 2.8 Ghz Xeon processors having 2 MB of cache for each, with the
> main memory of lets say 32 GB. We can either use a small SAN from EMC or we can put all disks
> into the machines with the required raid confiuration.
>
> We will install RedHat Advanced Server 2.1 to the machine as the operating system and postgresql as
> the database server. We have a database having 25 millions records having the length of 250 bytes
> on average for each record. And there are 1000 operators accessing the database concurrently. The main
> operation on the database (about 95%) is select rather than insert, so do you have any idea about
> the performance of the system?

Assumig 325 bytes per tuple(250 bytes field+24-28 byte header+varchar fields)
gives 25 tuples per 8K page, there would be 8GB of data. This configuration
could fly with 12-16GB of RAM. After all data is read that is. You can cut down
on other requirements as well. May be a 2x opteron with 16GB RAMmight be a
better fit but check out how much CPU cache it has.

A grep -rwn across data directory would fill the disk cache pretty well..:-)

HTH

Bye
Shridhar

--
Egotism, n: Doing the New York Times crossword puzzle with a pen.Egotist, n: A
person of low taste, more interested in himself than me. -- Ambrose Bierce,
"The Devil's Dictionary"