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Tuning system response degradation under heavy ext3/2 activity.



Hello.

 

I’m looking for assistance or pointers for the following problem.

OS: RHAS2.1 enterprise16

HW: HP proliant 2CPU 6GB RAM, internal RAID1 + RAID5(4 x 10K 72GB)

When we run any kind of process (especially tar for some reason) that creates heavy disk activity the machine becomes Very Slow, (e.g. takes 30-45 seconds to get a reply from ls at the console, or a minute to log in.)

I experimented with data="" and that made the box more responsive to other new processes, but naturally the io rate fell through the floor.

Also experimented with the elvtune, and we got very improved results for our tests (mainly scripts of dd, cp, and diff) but then apps (like tar) suffered.

(used elvtune –r 32 –w 32 gave the best numbers on the test scripts).

 

The best we can tell, the processing subsystem of the server is is way to fast for this relatively slow raid card.

During the test, io %util is always 100%, and the await and svc times hit 6 digits.

 

Is there anything else we can tune (such as scheduler behavior, etc) to mitigate this?

 

Thanks,

Dan

 

 

 


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