[CentOS] Re: Write performance with 3ware 9550

Scott Silva
Fri, 13 Oct 2006 20:22:05 -0000

Bowie Bailey spake the following on 10/12/2006 1:22 PM:
> 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!
>
Is there a difference in the write performance, speed, or cache size of the
drives?
You didn't list specifics of the drives, so I had to ask.

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