Re: Reports from SSD purgatory - Mailing list pgsql-performance

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Subject Re: Reports from SSD purgatory
Date
Msg-id 201108241942.061270@ms14.lnh.mail.rcn.net
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In response to Re: Reports from SSD purgatory  ("Tomas Vondra" <tv@fuzzy.cz>)
Responses Re: Reports from SSD purgatory  ("Tomas Vondra" <tv@fuzzy.cz>)
List pgsql-performance

---- Original message ----
>Date: Wed, 24 Aug 2011 21:32:16 +0200
>From: pgsql-performance-owner@postgresql.org (on behalf of "Tomas Vondra" <tv@fuzzy.cz>)
>Subject: Re: [PERFORM] Reports from SSD purgatory
>To: gnuoytr@rcn.com
>Cc: pgsql-performance@postgresql.org
>
>On 24 Srpen 2011, 20:48, gnuoytr@rcn.com wrote:
>
>> It's worth knowing exactly what that means.  Turns out that NAND quality
>> is price specific.  There's gooduns and baduns.  Is this a failure in the
>> controller(s) or the NAND?
>
>Why is that important? It's simply a failure of electronics and it has
>nothing to do with the wear limits. It simply fails without prior warning
>from the SMART.

It matters because if it's the controller, there's nothing one can do about it (the vendor).  If it's the NAND, then
thevendor/customer can get drives with gooduns rather than baduns.  Not necessarily a quick fix, but knowing the
qualityof the NAND in the SSD you're planning to buy matters. 
>
>> Also, given that PG is *nix centric and support for TRIM is win centric,
>> having that makes a big difference in performance.
>
>Windows specific? What do you mean? TRIM is a low-level way to tell the
>drive 'this block is empty and may be used for something else' - it's just
>another command sent to the drive. It has to be supported by the
>filesystem, though (e.g. ext4/btrfs support it).

My point.  The firmware and MS have been faster to support TRIM than *nix, linux in particular.  Those that won't/can't
moveto a recent kernel don't get TRIM. 

>
>Tomas
>
>
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