who can help me to find which process make the "IO Wait" so high?

[fishbed]

My system is IBM P570 whit oracle 9i RAC
I find that the “IO WAIT” always above 40% whit topas and many disks very busy for reading and writing.
But I can't find out which process make the "IO WAIT" so high.
Who can give me some suggestion?

 

[spamly]

Have you played with nmon? You can sort on processes based on a number of options.

http://www-128.ibm.com/developerworks/eserver/articles/analyze_aix/

 

[fishbed]

spamly:
Thanks a lot.
I had use nmon tool to get more infomation about my processes.
Other question, can you tell me about the concept of the "IO Wait" ?

 

[RodKnowlton]

IO Wait is any idle time during which there is an i/o pending. It's not always a bad sign, such as with a disk intensive application that doesn't require a lot of processor (like an OLTP database).

As processors get faster and faster and disks (relatively) don't, I'd expect to see more and more IO Wait. As long as your disks are 100% busy and you also see some actual Idle cpu, it's nothing to worry about. If you do have either of those symptoms, you need to improve the performance of your disk subsystem.



Rod Knowlton
IBM Certified Advanced Technical Expert pSeries and AIX 5L
CompTIA Linux+
CompTIA Security+

 

[kHz]

You don't want your disks 100% busy. That would be like saying you want your CPUs pegged at 100%. Talk about slow I/O.

 

[RodKnowlton]

s/are/aren't/

Sheesh.



Rod Knowlton
IBM Certified Advanced Technical Expert pSeries and AIX 5L
CompTIA Linux+
CompTIA Security+

 

[SLG]

Check out "filemon". It will tell you everything you want to know about what is going on with I/O on your system.

 

[fishbed]

thanks a lot

 

[fishbed]

Check out "filemon". It will tell you everything you want to know about what is going on with I/O on your system.

--But whit the trace report only I can only find out the busy disk and lv. The report file not include process infomation.