Grant,
Yes this is correct. If host A goes belly up, you can deassign the LUN
from host A and assign to
host B. Being that host A has not gracefully exported it's zpool you
will need to 'zpool import -f <poolname>'
to force the pool to be imported because it hasn't been exported prior
to import due to the unexpected inaccessibility
of host A.
It is possible to have the LUN visible to both machines at the same
time, just not in use by both machines. This
is in general how clusters work. Be aware that if you do do this and
access the disk on both systems then you run
a very real risk of corruption of the volume.
I use the first approach here quite regularly in what I call 'poor mans
clustering'. ;) I tend to install all my software
and data environments on SAN based LUNS that allow ease of moving just
by exporting the zpool , reassigning
the LUN then importing to the new system. Works well as long as both
systems are of the same OS revision
or greater on the target system.
/Scott.
Grant Lowe wrote:
Hi Erik,
A couple of questions about what you said in your email. In synopsis 2, if
hostA has gone belly up and is no longer accessible, then a step that is
implied (or maybe I'm just inferring it) is to go to the SAN and reassign the
LUN from hostA to hostB. Correct?
----- Original Message ----
From: Erik Trimble <[email protected]>
To: Grant Lowe <[email protected]>
Cc: [email protected]
Sent: Wednesday, March 11, 2009 1:42:06 PM
Subject: Re: [zfs-discuss] ZFS on a SAN
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.
(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>'
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.
-Erik
On Wed, 2009-03-11 at 13:18 -0700, Grant Lowe wrote:
Hi All,
I'm new on ZFS, so I hope this isn't too basic a question. I have a host where
I setup ZFS. The Oracle DBAs did their thing and I know have a number of ZFS
datasets with their respective clones and snapshots on serverA. I want to
export some of the clones to serverB. Do I need to zone serverB to see the
same LUNs as serverA? Or does it have to have preexisting, empty LUNs to
import the clones? Please help. Thanks.
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_______________________________________________________________________
Scott Lawson
Systems Architect
Manukau Institute of Technology
Information Communication Technology Services Private Bag 94006 Manukau
City Auckland New Zealand
Phone : +64 09 968 7611
Fax : +64 09 968 7641
Mobile : +64 27 568 7611
mailto:[email protected]
http://www.manukau.ac.nz
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$i=pack(c5,(41*2),sqrt(7056),(unpack(c,H)-2),oct(115),10);'
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