afaik for replication you will need at least three nodes.
ZFS is really cool, the downside is, you’ll need much more RAM for ZFS.
As a rule of thumb (don’t know if this is correct english, he he) you will need 1GByte RAM per TByte HDD space (exclusive for ZFS, so a machine with 12TByte HDD space will need at least 16GByte RAM to work properly, but you will have no space for some VMs)
My next server shall have about 24TByte HDD space, so 32GByte is maybe not enough anymore. Needless to say, ECC is a must have, but we’re talking about servers…