Re: Storing data and indexes in different disks

I'd say it's a little early to worry about a 10% performance increase
when you don't have any redundancy.  You might want to consider using
more, cheaper SATA disks - with more spindles you may very well get
better performance in addition to redundancy.

Anyway, here's an optimization project I just went through recently: the
old database was running all on a SAN attached RAID5 partition; moved
the indices to a local striped mirror set (faster disks too: 15K rpm),
moved the WAL files to a separate local two disk mirror, and spent a lot
of time tuning the config parameters (the old install was running the
conservative defaults).  All the hardware (apart from the additional
disks) is the same.  For some simple queries I saw as much as a 150X
speedup, though that's certainly not typical of the performance
improvement overall.  Most of this is likely due to the memory settings,
but faster disks certainly play a part.

In any case, it's hard to say what would improve performance for you
without knowing what kind of applications you are running and what sort
of load they see.

Dmitri

-----Original Message-----
From: pgsql-performance-owner@postgresql.org
[mailto:pgsql-performance-owner@postgresql.org] On Behalf Of Alvaro
Nunes Melo
Sent: Wednesday, July 06, 2005 1:59 PM
To: PostgreSQL - Performance
Subject: [PERFORM] Storing data and indexes in different disks


Hi,

I'm about to recommend a server model to a client, and I've read a in
many places (including in this list) that  storing indexes in one disk
and the rest of the database in other disk might increase the overall
performance  of the system in about 10%.

Making this only by a symbolic link is enough, or there are any futher
steps? We were thinking (for costs reasons) in use only 2 SCSI disks,
without any level of RAID. Is this enough to achieve performance
improvement mentioned above?

Best regards,
Alvaro

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