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Message-ID: <4D9204E9.1060403@krogh.cc>
Date: Tue, 29 Mar 2011 18:12:25 +0200
From: Jesper Krogh <jesper@krogh.cc>
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To: pgsql-performance@postgresql.org
Subject: Re: Intel SSDs that may not suck
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On 2011-03-29 16:16, Jeff wrote:
>  halt for 0.5-2 seconds, then resume. The fix we're going to do is
>  replace each drive in order with the rebuild occuring between each.
>  Then we do a security erase to reset the drive back to completely
>  empty (including the "spare" blocks kept around for writes).

Are you replacing the drives with new once, or just secure-erase and 
back in?
What kind of numbers are you drawing out of smartmontools in usage figures?
(Also seeing some write-stalls here, on 24 Raid50 volumes of x25m's, and
have been planning to cycle drives for quite some time, without actually
getting to it.

>  Now that all sounds awful and horrible until you get to overall
>  performance, especially with reads - you are looking at 20k random
>  reads per second with a few disks. Adding in writes does kick it
>  down a noch, but you're still looking at 10k+ iops. That is the
>  current trade off.

Thats also my experience.
-- 
Jesper

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    On 2011-03-29 16:16, Jeff wrote:<br>
    <span style="white-space: pre;">&gt; halt for 0.5-2 seconds, then
      resume. The fix we're going to do is<br>
      &gt; replace each drive in order with the rebuild occuring between
      each.<br>
      &gt; Then we do a security erase to reset the drive back to
      completely<br>
      &gt; empty (including the "spare" blocks kept around for writes).<br>
    </span><br>
    Are you replacing the drives with new once, or just secure-erase and
    back in? <br>
    What kind of numbers are you drawing out of smartmontools in usage
    figures? <br>
    (Also seeing some write-stalls here, on 24 Raid50 volumes of x25m's,
    and <br>
    have been planning to cycle drives for quite some time, without
    actually <br>
    getting to it. <br>
    <br>
    <span style="white-space: pre;">&gt; Now that all sounds awful and
      horrible until you get to overall<br>
      &gt; performance, especially with reads - you are looking at 20k
      random<br>
      &gt; reads per second with a few disks. Adding in writes does kick
      it<br>
      &gt; down a noch, but you're still looking at 10k+ iops. That is
      the<br>
      &gt; current trade off.<br>
      <br>
    </span>Thats also my experience. <br>
    -- <br>
    Jesper<br>
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