From: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>
To: Strahinja Kustudić <strahinjak@nordeus.com>
To: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: 8xIntel S3500 SSD in RAID10 on Dell H710p
Date: Wed, 10 Dec 2014 16:55:14 +1300
Message-ID: <5487C422.2000306@catalyst.net.nz> (raw)
In-Reply-To: <CADKbJJXupGHhwJvYHCgDJeNnm-DHjAQh5RjbTVgwWK1nza2ubQ@mail.gmail.com>
References: <CADKbJJXupGHhwJvYHCgDJeNnm-DHjAQh5RjbTVgwWK1nza2ubQ@mail.gmail.com>
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On 10/12/14 12:28, Strahinja Kustudić wrote:
> * These tests are with the H710p controller set to write-back (WB) and
> with adaptive read ahead (ADRA). I ran a few tests with
> write-through (WT) and no read ahead (NORA), but the results were worse.
That is interesting: I've done some testing on this type of card with 16
(slightly faster Hitachi) SSD attached. Setting WT and NORA should
enable the so-called 'fastpath' mode for the card [1]. We saw
performance improve markedly (300MB/s random write go to 1300MB/s).
This *might* be related to the fact that 16 SSD can put out more IOPS
than the card can actually handle - whereas your 8 S3500 is probably the
perfect number (e.g 8*11000 = 88000 which the card can handle ok).
[1] If you make the change while there are no outstanding background
operations (array rebuild etc) in progress (see
http://www.flagshiptech.com/eBay/Dell/poweredgeh310h710h810UsersGuide.pdf).
Cheers
Mark
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To: pgsql-performance@postgresql.org
Cc: mark.kirkwood@catalyst.net.nz, strahinjak@nordeus.com
Subject: Re: 8xIntel S3500 SSD in RAID10 on Dell H710p
In-Reply-To: <5487C422.2000306@catalyst.net.nz>
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