Highly available ZFS SAN/NAS with SMB and NFS
Unfortunately, I don't think you will be able to cluster them in the normal sense as zfs is not a clustered fs. Look at zfs snapshotting as a way to replicate your data. I believe the commands are zfs send and zfs recv.
ZFS isn't a cluster-aware file system unfortunately which limits its use in an instantaneous fail-over server cluster. However if your platform can afford a few seconds outage/pause then perhaps something like NexentaStor can be configured to be fairly highly available for a reasonable cost - it's very simple to setup and manage too.