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Re: Advice on RAID card

From: Greg Stark <gsstark(at)mit(dot)edu>
To: PFC <lists(at)boutiquenumerique(dot)com>
Cc: "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>,"Dave Cramer" <pg(at)fastcrypt(dot)com>,"Michael Ben-Nes" <miki(at)canaan(dot)co(dot)il>,pgsql-performance(at)postgresql(dot)org
Subject: Re: Advice on RAID card
Date: 2005-09-25 17:41:06
Message-ID: 873bntjb9p.fsf@stark.xeocode.com (view raw or flat)
Thread:
Lists: pgsql-performance
PFC <lists(at)boutiquenumerique(dot)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


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