performance counters on a SAN

Hello,
Recently we moved our database servers onto a emc cx600 san. Since
the move I ran perfmon against the server for a week to try to get a
baseline of the server's performance. I am getting some curious
metrics from perfmon on the avg. disk queue lenth and %disk time for
the data drive for the sql server database. We have the same
dedicated spindle config as we did on our former system with the
difference being the greatly increased throughput of the new system.
Avg. disk queue lenth is reporting an avg. of over 30 for lengthy
periods of time(> 10 minutes) and %disk time is reporting an avg of
over 300 around the same time . The former system was not reporting
any performance bottlenecks. I wonder if the counters are skewed
somehow. Has anyone experienced any oddities with disk related
performance counter metrics on a san or am I suddenly looking at a
disk bottleneck? Is it possible that the increased throughput to the
san is now causing a disk bottleneck?
Let me know if more details are needed.
Thanks,
GregThanks for the reply. The logical drive is a 10 spindle raid 5, so
the avg. disk queue length would be 3. If I'm not mistaken an avg.
disk queue length of 2 or more for any extended period of time would
be considered a bottleneck. Also, a % disk time of 300 seems rather
high to me as well. I am just curious if these disk counters report
accurately on a san as there weren't any bottlenecks reported on the
former system which was much slower than this system all the way
around. To my knowledge there hasn't been a substantial change in
workload to suddenly cause this.
Greg
On Tue, 12 Aug 2003 05:26:31 -0400, "Wayne Snyder"
<wsnyder@.computeredservices.com> wrote:
>Remember that disk queue lengths are for the logical drive... and to get
>*real* number you care about divide 30 by the number of physical drives
> which are likely to be a larger number in the SAN)...
>"Greg" <gjackson@.thq.com> wrote in message
>news:gjagjvgsp8ogelufmret27pdddi7vi4sh4@.4ax.com...
>> Hello,
>> Recently we moved our database servers onto a emc cx600 san. Since
>> the move I ran perfmon against the server for a week to try to get a
>> baseline of the server's performance. I am getting some curious
>> metrics from perfmon on the avg. disk queue lenth and %disk time for
>> the data drive for the sql server database. We have the same
>> dedicated spindle config as we did on our former system with the
>> difference being the greatly increased throughput of the new system.
>> Avg. disk queue lenth is reporting an avg. of over 30 for lengthy
>> periods of time(> 10 minutes) and %disk time is reporting an avg of
>> over 300 around the same time . The former system was not reporting
>> any performance bottlenecks. I wonder if the counters are skewed
>> somehow. Has anyone experienced any oddities with disk related
>> performance counter metrics on a san or am I suddenly looking at a
>> disk bottleneck? Is it possible that the increased throughput to the
>> san is now causing a disk bottleneck?
>> Let me know if more details are needed.
>> Thanks,
>> Greg
>sql