From: Greg Smith <greg@2ndQuadrant.com>
To: pgsql-performance@postgresql.org, Merlin Moncure <mmoncure@gmail.com>
Subject: Re: SSD selection
Date: Mon, 28 May 2012 08:14:05 -0400
Message-ID: <4FC36C0D.5090200@2ndQuadrant.com> (raw)
In-Reply-To: <CAHyXU0y6yrDL6NwBEC_DLDEQoqsyfj8i-p2iOP71--vSzZpZTg@mail.gmail.com>
References: <CABWW-d032_BBZCi-z5=1H-4SrytKEtE10=TAu3uOTa-BnHUU6Q@mail.gmail.com>
<CAFnxYwg8dMW_bihikwd8BNJBn_vN7wJB9nHe9umAdS3QWhHVcA@mail.gmail.com>
<4FB2B5C8.7030109@boreham.org>
<CAHyXU0y6yrDL6NwBEC_DLDEQoqsyfj8i-p2iOP71--vSzZpZTg@mail.gmail.com>
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
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To: pgsql-performance@postgresql.org
Cc: greg@2ndQuadrant.com, mmoncure@gmail.com
Subject: Re: SSD selection
In-Reply-To: <4FC36C0D.5090200@2ndQuadrant.com>
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