Message-ID: <4FC36C0D.5090200@2ndQuadrant.com>
Date: Mon, 28 May 2012 08:14:05 -0400
From: Greg Smith <greg@2ndQuadrant.com>
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To: pgsql-performance@postgresql.org, Merlin Moncure <mmoncure@gmail.com>
Subject: Re: SSD selection
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On 05/16/2012 01:01 PM, Merlin Moncure wrote:
> Although your assertion 100% supported by intel's marketing numbers,
> there are some contradicting numbers out there that show the drives
> offering pretty similar performance.  For example, look here:
> http://www.anandtech.com/show/4902/intel-ssd-710-200gb-review/4 and
> you can see that 4k aligned writes are giving quite similar results
> (14k iops) even though the 710 is only rated for 2700 iops while the
> 320 is rated for 21000 IOPS.  Other benchmarks also show similar
> results.

I wrote something talking about all the ways the two drives differ at 
http://blog.2ndquadrant.com/intel_ssds_lifetime_and_the_32/

What the 710 numbers are saying is that you can't push lots of tiny 
writes out at a high IOPS without busting the drive's lifetime 
estimates.  You can either get a really high IOPS of small writes (320) 
or a smaller IOPS of writes that are done more efficiently in terms of 
flash longevity (710).  You can't get both at the same time.  The 710 
may ultimately throttle its speed back to meet lifetime specifications 
as the drive fills, it's really hard to benchmark the differences 
between the two series.

-- 
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.com