Erik Trimble wrote:
I'm not 100% sure what your question here is, but let me give you a
(hopefully) complete answer:
(1) ZFS is NOT a clustered file system, in the sense that it is NOT
possible for two hosts to have the same LUN mounted at the same time,
even if both are hooked to a SAN and can normally see that LUN.
Need to be clear on the terminology here. Yes, it is possible for two
systems to have access to a single LUN and have ZFS file systems.
The ZFS limitation is at the vdev level (partition or slice), which is
below the LUN level.
(2) ZFS can do failover, however. If you have a LUN from a SAN on
hostA, create a ZFS pool in it, and use as normal. Should you with to
failover the LUN to hostB, you need to do a 'zpool export <zpool>' on
hostA, then 'zpool import <zpool>' on hostB. If hostA has been lost
completely (hung/died/etc) and you are unable to do an 'export' on it,
you can force the import on hostB via 'zpool import -f <zpool>'
LUN masking or reservations occur at the LUN level, which is why it is
often better (safer) to design with the expectation that a LUN will be
only available to one host at a time. Or, to say it differently, if you
think
of one vdev/LUN, then you can innoculate yourself from later grief :-)
ZFS requires that you import/export entire POOLS, not just filesystems.
So, given what you seem to want, I'd recommend this:
On the SAN, create (2) LUNs - one for your primary data, and one for
your snapshots/backups.
On hostA, create a zpool on the primary data LUN (call it zpool A), and
another zpool on the backup LUN (zpool B). Take snapshots on A, then
use 'zfs send' and 'zfs receive' to copy the clone/snapshot over to
zpool B. then 'zpool export B'
On hostB, import the snapshot pool: 'zfs import B'
It might just be as easy to have two independent zpools on each host,
and just do a 'zfs send' on hostA, and 'zfs receive' on hostB to copy
the snapshot/clone over the wire.
+1
-- richard
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