From: David Boreham <david_list@boreham.org>
To: pgsql-performance@postgresql.org
Subject: Re: Intel 320 SSD info
Date: Wed, 24 Aug 2011 11:23:15 -0600
Message-ID: <4E553383.80106@boreham.org> (raw)
In-Reply-To: <CAHyXU0zvtTXT9w897QH+tR9xpYYAnw-nLwK09edZh=nA-3tWbg@mail.gmail.com>
References: <4E552DCF.80802@boreham.org>
<CAHyXU0zvtTXT9w897QH+tR9xpYYAnw-nLwK09edZh=nA-3tWbg@mail.gmail.com>
On 8/24/2011 11:17 AM, Merlin Moncure wrote:
>
> hm, I think they need to reconcile those numbers with the ones on this
> page: http://www.intel.com/content/www/us/en/solid-state-drives/solid-state-drives-320-series.html
>
> 600 write ips vs 3.7k/23k.
>
>
They do provide an explanation (and what I find interesting about this
document is that they are basically "coming clean" about the real
worst-case performance, which I personally find refreshing and
encouraging). The difference is that the high number is achieved if the
drive does not need to perform a block erase to process the write (this
is true most of the time since the capacity is over-provisioned and
there is an expectation that GC will have generated free blocks in the
background). The low number is the performance under worst-case
conditions where the drive is a) full and b) no blocks have been
trimmed, and c) GC wasn't able to run yet.
I suspect that in production use it will be possible to predict in
advance when the drive is approaching the point where it will run out of
free blocks, and hence perform poorly. Whether or not this is possible
is a big question for us in planning our transition to SSDs in production.
Anyone using SSDs should be aware of how they work and the possible
worst case performance. This article helps with that !
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To: pgsql-performance@postgresql.org
Cc: david_list@boreham.org
Subject: Re: Intel 320 SSD info
In-Reply-To: <4E553383.80106@boreham.org>
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