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Two hard drives --- what to do with them?

From: Carlos Moreno <moreno_pg(at)mochima(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Two hard drives --- what to do with them?
Date: 2007-02-25 03:39:09
Message-ID: 45E104DD.3080600@mochima.com (view raw or flat)
Thread:
Lists: pgsql-performance
Say that I have a dual-core processor  (AMD64), with, say, 2GB of memory
to run PostgreSQL 8.2.3 on Fedora Core X.

I have the option to put two hard disks (SATA2, most likely);  I'm 
wondering
what would be the optimal configuration from the point of view of 
performance.

I do have the option to configure it in RAID-0, but I'm sort of 
reluctant;  I think
there's the possibility that having two filesystems that can be accessed 
truly
simultaneously can be more beneficial.  The question is:  does PostgreSQL
have separate, independent areas that require storage such that performance
would be noticeably boosted if the multiple storage operations could be 
done
simultaneously?

Notice that even with RAID-0, the "twice the performance" may turn into
an illusion --- if the system requires access from "distant" areas of 
the disk
("distant" as in  many tracks apart), then the back-and-forth travelling of
the heads would take precedence over the doubled access speed ...  Though
maybe it depends on whether accesses are in small chunks  (in which case
the cache of the hard disks could take precedence).

Coming back to the option of two independent disks --- the thing is:  if it
turns out that two independent disks are a better option, how should I
configure the system and the mount points?  And how would I configure
PostgreSQL to take advantage of that?

Advice, anyone?

Thanks,

Carlos
--


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