Gmirror/graid or hardware raid?

[Quartz]

> I thought about zfs but I won't have lots of RAM avaliable.

ZFS doesn't technically NEED gobs of ram just to function, that's a long 
standing urban myth repeated by people who don't understand how the ARC 
and/or dedupe works. You can run ZFS on basically any system, it's just 
a question of how much it can cache. The less it can cache the more it 
will have to hit the disks.... but that applies to basically every 
filesystem.

As for raid level, you only have four disks so you don't have a lot of 
options. You're pretty much looking at a raid-1, raid-10 or 
raid-5/raidz-1. A 4-way raid-1 is I think overkill, and a bunch of VMs 
will be heavy on the random read/write so a raid-5/raidz-1 will be worse 
than a raid-10 performance wise. (Although with only a four disk array 
the difference probably won't be earth shattering, so if you really need 
the space a 5/z1 won't kill you).