Re: Ever Increasing IOWAIT

Ralph Mason wrote:
> We have a database running on a 4 processor machine.  As time goes by the IO
> gets worse and worse peeking at about 200% as the machine loads up.
>
> The weird thing is that if we restart postgres it’s fine for hours but over
> time it goes bad again.
>
> (CPU usage graph here HYPERLINK
> "http://www.flickr.com/photos/8347741@N02/502596262/"http://www.flickr.com/p
> hotos/8347741@N02/502596262/ )  You can clearly see where the restart
> happens in the IO area

I'm assuming here we're talking about that big block of iowait at about
4-6am?

I take it vmstat/iostat show a corresponding increase in disk activity
at that time.

The question is - what?
Does the number of PG processes increase at that time? If that's not
intentional then you might need to see what your applications are up to.

Do you have a vacuum/backup scheduled for that time? Do you have some
other process doing a lot of file I/O at that time?

> This is Postgres  8.1.4 64bit.

You'll want to upgrade to the latest patch release - you're missing 5
lots of bug-fixes there.

--
   Richard Huxton
   Archonet Ltd