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Re: With 4 disks should I go for RAID 5 or RAID 10

From: david(at)lang(dot)hm
To: Mark Mielke <mark(at)mark(dot)mielke(dot)cc>
Cc: Florian Weimer <fw(at)deneb(dot)enyo(dot)de>, Fernando Hevia <fhevia(at)ip-tel(dot)com(dot)ar>, "'pgsql-performance'" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: With 4 disks should I go for RAID 5 or RAID 10
Date: 2007-12-26 23:05:50
Message-ID: Pine.LNX.4.64.0712261504310.11785@asgard.lang.hm (view raw or flat)
Thread:
Lists: pgsql-performance
On Wed, 26 Dec 2007, Mark Mielke wrote:

> 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.

except for raid0, raid is primarily a reliability benifit, any performance 
benifit is incidental, not the primary purpose.

that said, I have heard of raid1 setups where it only reads off of one of 
the drives, but I have not heard of higher raid levels doing so.

David Lang

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