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Comments requested on IO performance : new db server

From: Rory Campbell-Lange <rory(at)campbell-lange(dot)net>
To: pgsql-performance(at)postgresql(dot)org
Subject: Comments requested on IO performance : new db server
Date: 2012-03-09 11:15:58
Message-ID: 20120309111558.GA22643@campbell-lange.net (view raw or flat)
Thread:
Lists: pgsql-performance
I've taken the liberty of reposting this message as my addendum to a
long thread that I started on the subject of adding a new db server to
our existing 4-year old workhorse got lost in discussion.

Our workload is several small databases totalling less than 40GB of disk
space. The proposed system has 48GB RAM, 2 * quad core E5620 @ 2.40GHz
and 4 WD Raptors behind an LSI SAS card. Our supplier has just run a set
of tests on the machine we intend to buy. The test rig had the following
setup:

LSI MegaRAID SAS 9260-8i
Firmware: 12.12.0-0090
Kernel: 2.6.39.4
Hard disks: 4x WD6000BLHX
Test done on 256GB volume
BS = blocksize in bytes

The test tool is fio. I'd be grateful to know if the results below are
considered acceptable. An ancillary question is whether a 4096 block
size is a good idea. I suppose we will be using XFS which I understand
has a default block size of 4096 bytes. 

RAID 10
--------------------------------------
Read sequential

    BS           MB/s             IOPs
   512        0129.26        264730.80
  1024        0229.75        235273.40
  4096        0363.14        092965.50
 16384        0475.02        030401.50
 65536        0472.79        007564.65
131072        0428.15        003425.20
--------------------------------------
Write sequential

    BS           MB/s             IOPs
   512        0036.08        073908.00
  1024        0065.61        067192.60
  4096        0170.15        043560.40
 16384        0219.80        014067.57
 65536        0240.05        003840.91
131072        0243.96        001951.74
--------------------------------------
Random read

    BS           MB/s             IOPs
   512        0001.50        003077.20
  1024        0002.91        002981.40
  4096        0011.59        002968.30
 16384        0044.50        002848.28
 65536        0156.96        002511.41
131072        0170.65        001365.25
--------------------------------------
Random write

    BS           MB/s             IOPs
   512        0000.53        001103.60
  1024        0001.15        001179.20
  4096        0004.43        001135.30
 16384        0017.61        001127.56
 65536        0061.39        000982.39
131072        0079.27        000634.16
--------------------------------------


-- 
Rory Campbell-Lange
rory(at)campbell-lange(dot)net

Campbell-Lange Workshop
www.campbell-lange.net
0207 6311 555
3 Tottenham Street London W1T 2AF
Registered in England No. 04551928

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Subject: Tuning wizard
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Subject: Re: Advice sought : new database server

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