Originally posted by: karunanidhis

Hi All !
We have an issue with our AIX 5.3 System where in a disk becomes 100% busy exactly at 15 minute intervals with LESSER IO and HIGHER WRITE TIME (observed from filemon output). The 'lesser' i/o is probably is the result of 'higher' write time. The issue lasts for about 20 seconds. The disk is EMC Symmertix SAN disk. We see a slight CPU spike also during this time. We took numerous traces, nmon, topas etc. All traces are pointing to the symptoms but none pointing to the root cause. We had disabled cron daemon but it did not help.

Has anyone encountered a similar isssue ?

Thanks for your help.
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Originally posted by: niella

Hi,

You could perhaps start by checking your level of PowerPath. We recently had a problem where topas would show 100% wait but with very little actual activity.

After upgrading to PowerPath 5.3.1.0 (5.3 SP1), these problems disappeared and I understand it to relate to the following as per the s/w release notes (300-010-389.pdf):

302444
Double counting of statistics occurs when PowerPath is registered as physical disk in the AIX platform.

If that does not help, you should post the actual output of say ''filemon -dPo filemon.out -O lf,lv,pv -T 10485760" over the problem period.

Niel
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