recommended memory for zfs

[Benjamin Adams]

Hello zfs question about memory.
I heard zfs is very ram hungry.
Service looking to run:
- nginx
- postgres
- php-fpm
- python

I have a machine with two quad core cpus but only 4 G Memory

I'm looking to buy more ram now.
What would be the recommend amount of memory for zfs across 6 drives on 
this setup?


Also can 9.1 now boot to zfs from the installer?
(no tricks for post install)

Thanks
Ben