Received: from localhost (unknown [200.46.204.182])
	by postgresql.org (Postfix) with ESMTP id 834BA2E2F8E
	for <pgsql-performance-postgresql.org@postgresql.org>;
	Wed, 26 Dec 2007 18:02:59 -0400 (AST)
Received: from postgresql.org ([200.46.204.71])
	by localhost (mx1.hub.org [200.46.204.182]) (amavisd-maia, port 10024)
	with ESMTP id 69216-05 for
	<pgsql-performance-postgresql.org@postgresql.org>;
	Wed, 26 Dec 2007 18:02:50 -0400 (AST)
Received: from ironport2-out.pppoe.ca (ironport2-out.pppoe.ca
	[206.248.154.182])
	by postgresql.org (Postfix) with ESMTP id C47D12E2F88
	for <pgsql-performance@postgresql.org>;
	Wed, 26 Dec 2007 18:02:52 -0400 (AST)
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: Ao8CAGNeckfO+Igp/2dsb2JhbACpSA
X-IronPort-AV: E=Sophos;i="4.24,209,1196658000"; d="scan'208";a="11989071"
Received: from smtp.pppoe.ca ([65.39.196.238])
	by ironport2-out.pppoe.ca with ESMTP; 26 Dec 2007 17:02:52 -0500
Received: from [206.248.136.41] ([206.248.136.41])
	by smtp.pppoe.ca (Internet Mail Server v1.0) with ESMTP id FIC80451;
	Wed, 26 Dec 2007 17:02:51 -0500
Message-ID: <4772CED1.2070808@mark.mielke.cc>
Date: Wed, 26 Dec 2007 16:59:45 -0500
From: Mark Mielke <mark@mark.mielke.cc>
User-Agent: Thunderbird 2.0.0.9 (X11/20071115)
MIME-Version: 1.0
To: david@lang.hm
CC: Florian Weimer <fw@deneb.enyo.de>, Fernando Hevia <fhevia@ip-tel.com.ar>,
	'pgsql-performance' <pgsql-performance@postgresql.org>
Subject: Re: With 4 disks should I go for RAID 5 or RAID 10
References: <0f8201c847f6$08e15090$8f01010a@iptel.com.ar>
	<Pine.LNX.4.64.0712261317320.11785@asgard.lang.hm>
	<87zlvxnpkl.fsf@mid.deneb.enyo.de>
	<Pine.LNX.4.64.0712261452410.11785@asgard.lang.hm>
In-Reply-To: <Pine.LNX.4.64.0712261452410.11785@asgard.lang.hm>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
X-Virus-Scanned: Maia Mailguard 1.0.1
X-Archive-Number: 200712/384
X-Sequence-Number: 28200

david@lang.hm wrote:
> I could see a raid 1 array not doing consistancy checking (after all, 
> it has no way of knowing what's right if it finds an error), but since 
> raid 5/6 can repair the data I would expect them to do the checking 
> each time.
Your messages are spread across the thread. :-)

RAID 5 cannot repair the data. I don't know much about RAID 6, but I 
expect it cannot necessarily repair the data either. It still doesn't 
know which drive is wrong. In any case, there is no implementation I am 
aware of that performs mandatory consistency checks on read. This would 
be silliness.

Cheers,
mark

-- 
Mark Mielke <mark@mielke.cc>