Performance problems with Postgresql/ZFS/Non-global zones on Solaris?

In the hopes that someone has already blazed this trail ...

I'm running Postgresql (v8.1.10) on Solaris 10 (Sparc) from within a non-global zone. I originally had the database "storage" in the non-global zone (e.g. /var/local/pgsql/data on a UFS filesystem) and was getting performance of "X" (e.g. from a TPC-like application: http://www.tpc.org). I then wanted to try relocating the database storage from the zone (UFS filesystem) over to a ZFS-based filesystem (where I could do things like set quotas, etc.). When I do this, I get roughly half the performance (X/2) I did on the UFS system. I did try to run some low level I/O tests (i.e. http://www.iozone.org/) to see if there was a filesystem performance difference, but there doesn't seem to be any between the UFS and ZFS numbers I'm seeing.

So, I was hoping someone might have already tried this type of setup and can provide some suggestions for helping boost the ZFS performance numbers (and save me a truss debugging session).

Are there any known issues with using Postgresql and ZFS?

Things I have already tried:

- setting the record size of the ZFS filesystem to be 8K (vs 128K ) default -- no noticeable performance difference

- addind the ZFS filesystem as a loopback (i.e. lofs) filesystem in the non-global zone -- no noticeable difference

- adding the ZFS filesystem as a dataset filesystem in the non-global zone -- no noticeable difference

Bob