Re: Debugging extreme disk IO latency

Åsmund Grammeltvedt wrote:
Hi.

I am running into some very nasty IO latency, using a Western Digital Caviar
Green 1.5TB (WD15EADS) with XFS. Adding one writer (cat /dev/zero | pv >
/tmp/foo) appears to cause a massive latency spike after ~10-20 minutes, where
almost no interaction, read or write, with the disk comes through. The spike
lasts for up to ~5 minutes, after which everything is back to normal.

Any ideas of what might be causing this or how to proceed with debugging this
issue would be much appreciated. Thanks.


Can you replicate this if you boot from a live CD? If yes, are you able
to run dmesg to see if there are any relevant messages during the spikes?

If you can reproduce the error with the BootCD, I would vet the drive
itself by testing on a different computer, if possible.



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