PostgreSQL on Solaris 8 and ufs

We've recently moved our pgsql installation and DBs to a Solaris 8
machine with striped and mirrored ufs filesystem that houses the DB
data.  We are now seeing terrible performance and the bottleneck is no
doubt disk I/O.

We've tried modifying a tunables related to ufs, but it doesn't seem
to be helping.

Is there anything we should be looking at that is specifically related
to ufs filesystems on Solaris 8 or possibly something in general that
would improve performance?

Thanks.

--
Brandon