I have two identical servers. The only difference is that the first
one has Maxtor 250G drives and the second one has Seagate 320G drives.
OS: CentOS-4.4 (fully patched)
CPU: dual Opteron 280
Memory: 16GB
Raid card: 3ware 9550Sx-8LP
Raid volume: 4-disk Raid 5 with NCQ and Write Cache enabled
On the first server I have decent performance. Nothing spectacular,
but good enough. The second one has about 1/3 the write speed. I
can't find any difference between the systems. Both of them have the
same stripe size, both have ext3 filesystems, both have write caching
and NCQ turned on. I have already increased the read ahead setting to
16384 on both servers.
I ran the tests like this:
# sync; bonnie++ -d /iotest -s 50g -n 0 -b -f
(I have removed some extra information from the reports for brevity)
And here are the results for the two servers:
------Output------- --Input--
--Block-- -Rewrite- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP /sec %CP
First 50G 62893 25 46763 12 160672 19 120.6 1
Second 50G 18835 7 44025 12 194719 24 122.8 1
As you can see, the write performance of the second server is
terrible. Anyone have any suggestions of what I can look for? I keep
thinking there must be something I tweaked on the first server that I
forgot about for the second one, but so far I haven't been able to
find it.
Any suggestions appreciated!
--
Bowie
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