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Re: Looking for a cheap upgrade (RAID)

From: "scott(dot)marlowe" <scott(dot)marlowe(at)ihs(dot)com>
To: Chad Thompson <chad(at)weblinkservices(dot)com>
Cc: pgsql-performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Looking for a cheap upgrade (RAID)
Date: 2003-05-02 20:04:37
Message-ID: Pine.LNX.4.33.0305021401030.24893-100000@css120.ihs.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Fri, 2 May 2003, Chad Thompson wrote:

> I have a server on a standard pc right now.
> PIII 700, 1Gig ram (SD), 40 Gig IDE, RedHat 8.0, PostgreSQL 7.3.1
> 
> The database has 3 tables that just broke 10 million tuples (yeah, i think
> im entering in to the world of real databases ;-)
> Its primarly bulk (copy) inserts and queries, rarely an update.
> 
> I am looking at moving this to a P4 2.4G, 2 Gig Ram(DDR), RedHat 8,
> PostgreSQL 7.3.latest
> 
> My primary reason for posting this is to help filter through the noise, and
> get me pointed in the right direction.
> 
> I realize that Im a raid on linux newbie so any suggestions are appreciated.
> Im thinking I want to put this on an IDE Raid array, probably 0+1. IDE seems
> to be cheap and effective these days.
> What ive been able to glean from other postings is that I should have 3
> drives, 2 for the database w/ striping and another for the WAL.
> Am I way off base here?
> I would also appreciate raid hardware suggestions (brands, etc)
> And as always im not afraid to RTFM if someone can point me to the FM :-)
> 
> Cost seems to be quite a high priority, I'm getting pretty good at making
> something out of nothing for everyone :)

My experience has been that with IDEs, RAID-5 is pretty good (85% the 
performance of RAID-1 in real use) X+0 in linux kernel (2.4.7 is what I 
tested, no idea on the newer kernel versions) is no faster than X where X 
is 1 or 5.  I think there are parallel issues with stacking with linux 
software kernel arrays.  That said, their performance in stock RAID1 and 
RAID5 configurations is quite good.

If your writes happen during off hours, or only account for a small 
portion of your IO then a seperate drive is not gonna win you much, it's a 
heavily written environment that will gain from that.


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Subject: Re: Looking for a cheap upgrade (RAID)
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