Hi,
Want to let everyone know what we found out. I worked with the SAN
vendor to determine that the SAN was running fine although we did find
one setting incorrect on the hosts. If you run iSCSI you need to make
sure you disable the Nagle Algorithm on your hosts as it can cause
delays. A concise description is:
http://social.technet.microsoft.com/wiki/contents/articles/7636.iscsi-and-the-nagle-algorithm.aspx
So we did this and still no real change. Then we started looking deeper
at the data and noticed that the read delays happened every 10 minutes
h:00, h:10, h:20... and the rest of the time the were no reads at all on
the transaction log directory. Hmm what process could be reading from
the logs directory every 10 minutes. A few minutes later we figured out
that a process was set up to copy the transaction logs off to a backup
server every 10 minutes.
The reason it looked like we had very bad read response times on a daily
basis was that the monitoring tool took measurements every 10 minutes
for daily readings and just picked up the high points ignoring all the
low points in between.
End result is that the response time issue is an artifact of the
monitoring tool data collection methodology not a real problem. Lesson
learned is that when I see strangeness I need to really understand how I
collected the data showing the strangeness.
Thanks to everyone who replied and I hope this helps someone else.
cheers,
skib
--
"When we try to pick out anything by itself, we find it
connected to the entire universe" John Muir
Chris "Ski" Kacoroski, [email protected], 206-501-9803
or ski98033 on most IM services
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