Vacuum wait time problem

Hi,

I'm running vacuum full analyze verbose on a table with 20million rows
and 11 indexes.  In top, I'm seeing [pdflush] and postgres: writer
process each using diferent cpu cores, with wait time well above 90% on
each of them.  The vacuum has been running for several hours, and the
last thing to show on screen, over an hour ago, was :

DETAIL:  8577281 index row versions were removed.
736 index pages have been deleted, 736 are currently reusable.
CPU 7.57s/52.52u sec elapsed 381.70 sec.

That's the last index

The vacuum process itself is using less than 2% of a core.
The pg version is 8.3.1 running on Suse.  Hardware is 2X dual core
Opterons, 16 GB RAM, 24 drives in RAID 50

It would seem to me that the system is extremely IO bound, but I don't
know how to find out what specifically is wrong here.  Any advice
greatly appreciated.

--
Roger Ging

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