How to tell if linux disk IO is causing excessive (> 1 second) application stalls

Posted by noahz on Server Fault See other posts from Server Fault or by noahz
Published on 2012-11-09T23:36:33Z Indexed on 2012/11/12 23:03 UTC
Read the original article Hit count: 274

Filed under:

linux

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Performance

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redhat

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san

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veritas

I have a Java application performing a large volume (hundreds of MB) of continuous output (streaming plain text) to about a dozen files a ~~ext3~~ SAN filesystem. Occasionally, this application pauses for several seconds at a time. I suspect that something related to ~~ext3~~ vsfs (Veritas Filesystem) functionality (and/or how it interacts with the OS) is the culprit.

What steps can I take to confirm or refute this theory? I am aware of iostat and /proc/diskstats as starting points.

Revised title to de-emphasize journaling and emphasize "stalls"

I have done some googling and found at least one article that seems to describe behavior like I am observing: Solving the ext3 latency problem

Additional Information

Red Hat Enterprise Linux Server release 5.3 (Tikanga)
Kernel: 2.6.18-194.32.1.el5
Primary application disk is fiber-channel SAN: lspci | grep -i fibre >> 14:00.0 Fibre Channel: Emulex Corporation Saturn-X: LightPulse Fibre Channel Host Adapter (rev 03)
Mount info: type vxfs (rw,tmplog,largefiles,mincache=tmpcache,ioerror=mwdisable) 0 0
cat /sys/block/VxVM123456/queue/scheduler >> noop anticipatory [deadline] cfq

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