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High I/O wait in apache tomcat server

cn flag

Facing high I/O wait in apache tomcat server when the load increases. Suspecting disk I/O is less when tomcat is running however. disk IO seems drops drastically when tomcat is running along with the load. Other resources(CPU,RAM) are under utilized. Unable to find the reason. Kindly suggest.

IMAGE IOSTAT IMAGE SAR

Gerrit avatar
cn flag
iotop, inotifywatch are nice tools. Also to trace all file systemcalls of tomcat, you could use `strace -p tomcat-pid -f -e trace=file -o output-file`. Is there perhaps some database application running inside tomcat that wants to log transactions? sdc seems to have the highest wait times. Is there any lvm or raid across the disks? Is tomcat the primary load of the machine?
Sandesh Bailur avatar
cn flag
No database appllication running inside the tomcat. Yes sdc is a lvm. and tomcat itself is the primary load of the machine.
Gerrit avatar
cn flag
The write throughput on sdc is considerable (depending on the hardware of course). To get a feeling for what is writing use iotop and jcmd from Java JDK. With `sudo -u tomcatuser jcmd pidoftomcat Thread.print` you can get a good idea of what actions Java is taking at that moment.
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