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Message-ID: <4772CA58.5050406@mark.mielke.cc>
Date: Wed, 26 Dec 2007 16:40:40 -0500
From: Mark Mielke <mark@mark.mielke.cc>
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To: Florian Weimer <fw@deneb.enyo.de>
CC: david@lang.hm, 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>
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Florian Weimer wrote:
>> seek/read/calculate/seek/write since the drive moves on after the
>> read), when you read you must read _all_ drives in the set to check
>> the data integrity.
>>     
> I don't know of any RAID implementation that performs consistency
> checking on each read operation. 8-(
>   

Dave had too much egg nog... :-)

Yep - checking consistency on read would eliminate the performance 
benefits of RAID under any redundant configuration.

Cheers,
mark

-- 
Mark Mielke <mark@mielke.cc>


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Florian Weimer wrote:
<blockquote cite="mid:87zlvxnpkl.fsf@mid.deneb.enyo.de" type="cite">
  <blockquote type="cite">
    <pre wrap="">seek/read/calculate/seek/write since the drive moves on after the
read), when you read you must read _all_ drives in the set to check
the data integrity.
    </pre>
  </blockquote>
  <pre wrap=""><!---->I don't know of any RAID implementation that performs consistency
checking on each read operation. 8-(
  </pre>
</blockquote>
<br>
Dave had too much egg nog... :-)<br>
<br>
Yep - checking consistency on read would eliminate the performance
benefits of RAID under any redundant configuration.<br>
<br>
Cheers,<br>
mark<br>
<br>
<pre class="moz-signature" cols="72">-- 
Mark Mielke <a class="moz-txt-link-rfc2396E" href="mailto:mark@mielke.cc">&lt;mark@mielke.cc&gt;</a>
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