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