Re: SAN performance mystery

Jeff Trout wrote:
> On Jun 16, 2006, at 5:11 AM, Tim Allen wrote:
>> One curious thing is that some postgres backends seem to spend an
>> inordinate amount of time in uninterruptible iowait state. I found  a
>> posting to this list from December 2004 from someone who reported
>> that very same thing. For example, bringing down postgres on the
>> customer box requires kill -9, because there are invariably one or
>> two processes so deeply uninterruptible as to not respond to a
>> politer signal. That indicates something not quite right, doesn't it?
>
> Sounds like there could be a driver/array/kernel bug there that is
> kicking the performance down the tube.
> If it was PG's fault it wouldn't be stuck uninterruptable.

That's what I thought. I've advised the customer to upgrade their kernel
drivers, and to preferably upgrade their kernel as well. We'll see if
they accept the advice :-|.

Tim

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Tim Allen          tim@proximity.com.au
Proximity Pty Ltd  http://www.proximity.com.au/