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Message-ID: <4E553407.6010608@boreham.org>
Date: Wed, 24 Aug 2011 11:25:27 -0600
From: David Boreham <david_list@boreham.org>
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To: pgsql-performance@postgresql.org
Subject: Re: Intel 320 SSD info
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	<1314206629.63488.YahooMailNeo@web111301.mail.gq1.yahoo.com>
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On 8/24/2011 11:23 AM, Andy wrote:
> According to the specs for database storage:
>
> "Random 4KB arites: Up to 600 IOPS"
>
> Is that for real? 600 IOPS is *atrociously terrible* for an SSD. Not 
> much faster than mechanical disks.
>
>
The underlying (Flash block) write rate really is terrible (and slower 
than most rotating disks).

The trick with SSD is that firmware performs all kinds of stunts to make 
the performance seen
by the OS much higher (most of the time !). This is akin to write-back 
caching in a raid controller,
for example, where much higher write rates than the physical drives 
support are achievable.



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    On 8/24/2011 11:23 AM, Andy wrote:
    <blockquote
      cite="mid:1314206629.63488.YahooMailNeo@web111301.mail.gq1.yahoo.com"
      type="cite">
      <div style="color:#000; background-color:#fff; font-family:times
        new roman, new york, times, serif;font-size:12pt">
        <div><span>According to the specs for database storage:</span></div>
        <div><span><br>
          </span></div>
        <div><span>"Random 4KB arites: Up to 600 IOPS"</span></div>
        <div><span><br>
          </span></div>
        <div><span>Is that for real? 600 IOPS is *atrociously terrible*
            for an SSD. Not much faster than mechanical disks.</span></div>
        <div><span><br>
          </span></div>
        <br>
      </div>
    </blockquote>
    The underlying (Flash block) write rate really is terrible (and
    slower than most rotating disks).<br>
    <br>
    The trick with SSD is that firmware performs all kinds of stunts to
    make the performance seen<br>
    by the OS much higher (most of the time !). This is akin to
    write-back caching in a raid controller,<br>
    for example, where much higher write rates than the physical drives
    support are achievable.<br>
    <br>
    <br>
  </body>
</html>

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