Comments requested on IO performance : new db server

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

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