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Re: SSD and RAID

From: Yeb Havinga <yebhavinga(at)gmail(dot)com>
To: Mark Kirkwood <mark(dot)kirkwood(at)catalyst(dot)net(dot)nz>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: SSD and RAID
Date: 2012-03-07 09:45:09
Message-ID: 4F572E25.1000307@gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On 2012-03-07 01:36, Mark Kirkwood wrote:
> On 06/03/12 21:17, Yeb Havinga wrote:
>>
>>
>> One thing to note is that linux software raid with md doesn't support 
>> discard, which might shorten the drive's expected lifetime. To get 
>> some numbers I tested the raid 1 of ssd's setup for mediawear under a 
>> PostgreSQL load earlier, see 
>> http://archives.postgresql.org/pgsql-general/2011-11/msg00141.php
>>
>>
>
> Right, which is a bit of a pain - we are considering either formatting 
> the drive with less capacity and using md RAID 1 or else doing the 
> mirror in LVM to enable a working discard/trim.

When I measured the write durability without discard on the enterprise 
disks, I got numbers that in normal production use would outlive the 
lifetime of the servers. It would be interesting to see durability 
numbers for the desktop SSDs, even when partitioned to a part of the disk.

regards,
Yeb Havinga


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