ZFS compression?

[Vincent Fox]

Has anyone attempted using ZFS compression on mail spools?

This is a new Cyrus 2.3.8 mail-store, and we are using dual fiber
HBA to SAN switches and Sun 3510FC units on the backend, multipath
and active-active on the dual-controllers.  RAID-5 LUNs on each array
are ZFS mirrored between arrays.  Yes, multiple levels of paranoia.
We have Sun T2000 which are quad-CPU.  So it seems like there is
plenty of CPU there for the extra overhead that inline compression is
likely to add.

Anyhow,  I still envision the I/O being the bottleneck though so I am
wondering if turning this on will buy me any performance and at what price?
This system is not in production yet so I am still throwing things at it
to see at what point it breaks.