No, we don't use it as a filesystem at all. Our product is similar to EBS. So, nothing is mounted anywhere. Users of our product will get a slice or a whole volume thus created and usually would put some filesystem on it, but they will see that volume as a LUN in iSCSI portal we give them an address of. So, in principle, they could also use it to create a ZFS filesystem, but I doubt anyone uses it like that. Most typical usages are either filesystem (something like Ext4 or XFS) or an object store.