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From: Decibel! <decibel@decibel.org>
To: pgsql-performance@postgresql.org
Subject: Re: SAN vs Internal Disks
Date: Tue, 11 Sep 2007 18:07:44 -0500
Message-ID: <20070911230744.GJ38801@decibel.org> (raw)
In-Reply-To: <20070911210857.GQ1795@mathom.us>
References: <a199704d0709060535q6fea139aq2e3863e685555b0d@mail.gmail.com>
	<dcc563d10709060925o6f11f632sbfbc2b64530ae80d@mail.gmail.com>
	<a199704d0709061003u71d536fbh9d71ed095dfe16b@mail.gmail.com>
	<Pine.GSO.4.64.0709062354040.28915@westnet.com>
	<20070907100446.GE1795@mathom.us>
	<20070907103341.GC20896@oppetid.no>
	<Pine.LNX.4.64.0709071400430.19737@asgard.lang.hm>
	<20070911205550.GA38801@decibel.org>
	<20070911210857.GQ1795@mathom.us>

On Tue, Sep 11, 2007 at 05:09:00PM -0400, Michael Stone wrote:
> On Tue, Sep 11, 2007 at 03:55:51PM -0500, Decibel! wrote:
> >Also, to reply to someone else's email... there is one big reason to use
> >a SAN over direct storage: you can do HA that results in 0 data loss.
> >Good SANs are engineered to be highly redundant, with multiple
> >controllers, PSUs, etc, so that the odds of losing the SAN itself are
> >very, very low. The same isn't true with DAS.
> 
> You can get DAS arrays with multiple controllers, PSUs, etc.  DAS != 
> single disk.

It's still in the same chassis, though, which means if you lose memory
or mobo you're still screwed. In a SAN setup for redundancy, there's
very little in the way of a single point of failure; generally only the
backplane, and because there's very little that's on there it's
extremely rare for one to fail.
-- 
Decibel!, aka Jim Nasby                        decibel@decibel.org
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)

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