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To: PFC <lists@boutiquenumerique.com>
Cc: "Joshua D. Drake" <jd@commandprompt.com>,
 "Dave Cramer" <pg@fastcrypt.com>,
	"Michael Ben-Nes" <miki@canaan.co.il>, pgsql-performance@postgresql.org
Subject: Re: Advice on RAID card
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In-Reply-To: <op.sxn3v7a1th1vuj@localhost>
From: Greg Stark <gsstark@mit.edu>
Organization: The Emacs Conspiracy; member since 1992
Date: 25 Sep 2005 13:41:06 -0400
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PFC <lists@boutiquenumerique.com> writes:

> 	Which makes me think that I will use Software Raid 5 and convert the
> price of the card into RAM.
> 	This should be nice for a budget server.
> 	Gonna investigate now if Linux software RAID5 is rugged enough. Can
> always buy the a card later if not.

Raid 5 is perhaps the exception here. For Raid 5 a substantial amount of CPU
power is needed.

Also, Raid 5 is particularly inappropriate for write-heavy Database traffic.
Raid 5 actually hurts write latency dramatically and Databases are very
sensitive to latency.

On the other hand if your database is primarily read-only then Raid 5 may not
be a problem and may be faster than raid 1+0.

-- 
greg