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Excessive i/o wait

 
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Sherbert Punt
Occasional Advisor

Excessive i/o wait

Greetings

I have an oracle box that yesterday when in very high i/o wait on the / partition oracle has seperate partitions

iostat and sar confirmed that yes there was high usage on the disk

There were no backups nor unexpected processes running I turned off hpasm and our monitoring software but no joy...

I suppose my question is how does one locate the culprit that caused this...

Thanking you
3 REPLIES
Steven E. Protter
Exalted Contributor
Solution

Re: Excessive i/o wait

Shalom,

I would stop and start the oracle database.

First place I would look would be at the database.

One ugly user interactive sql statement can be the cause of this.

Poor database layout could be it.

Its a fishing expedition. Take a look at disk layout. Look for index and rollback an data being on a raid 5 and being write intensive.

Look for hardware issues with the disk.

Keep looking until you find a cause.

SEP
Steven E Protter
Owner of ISN Corporation
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Goran Koruga
Honored Contributor

Re: Excessive i/o wait

Hi.

To find out which process is responsible for I/O you can use two methods:

1. Use blktrace tools (needs CONFIG_BLK_DEV_IO_TRACE kernel option)

2. Use block_dump method, explained in kernel docs (laptop-mode.txt) - turn off syslog etc. before enabling this.

Regards,
Goran
Sherbert Punt
Occasional Advisor

Re: Excessive i/o wait

Many thanks I shall test that out...

--Sherbert