ZFS FreeBSD + ZFS + PostgreSQL, need suggestions.

Requirement: Install a FreeBSD system with zfs, and then run PostgreSQL.

The system has two same hard disks, so I want a zfs mirror.

In order to improve the PostgreSQL performance, what should I do this with this:

Isn't UFS without softupdates the pro way? under postgresql...and then extents or something aligned like was it 8k or something.....