On Mon, Mar 15, 2010 at 9:55 AM, Gabriele Bulfon <gbul...@sonicle.com>wrote:
> Hello, > I'd like to check for any guidance about using zfs on iscsi storage > appliances. > Recently I had an unlucky situation with an unlucky storage machine > freezing. > Once the storage was up again (rebooted) all other iscsi clients were > happy, while one of the iscsi clients (a sun solaris sparc, running Oracle) > did not mount the volume marking it as corrupted. > I had no way to get back my zfs data: had to destroy and recreate from > backups. > So I have some questions regarding this nice story: > - I remember sysadmins being able to almost always recover data on > corrupted ufs filesystems by magic of superblocks. Is there something > similar on zfs? Is there really no way to access data of a corrupted zfs > filesystem? > - In this case, the storage appliance is a legacy system based on linux, so > raids/mirrors are managed at the storage side its own way. Being an iscsi > target, this volume was mounted as a single iscsi disk from the solaris > host, and prepared as a zfs pool consisting of this single iscsi target. ZFS > best practices, tell me that to be safe in case of corruption, pools should > always be mirrors or raidz on 2 or more disks. In this case, I considered > all safe, because the mirror and raid was managed by the storage machine. > But from the solaris host point of view, the pool was just one! And maybe > this has been the point of failure. What is the correct way to go in this > case? > - Finally, looking forward to run new storage appliances using OpenSolaris > and its ZFS+iscsitadm and/or comstar, I feel a bit confused by the > possibility of having a double zfs situation: in this case, I would have the > storage zfs filesystem divided into zfs volumes, accessed via iscsi by a > possible solaris host that creates his own zfs pool on it (...is it too > redundant??) and again I would fall in the same previous case (host zfs pool > connected to one only iscsi resource). > > Any guidance would be really appreciated :) > Thanks a lot > Gabriele. > > To answer the other portion of your question, yes, you can roll back zfs if you're at the proper version. The procedure is listed below, essentially it will try to find the last known good transaction. If that doesn't work, your only remaining option is to restore from backup: http://docs.sun.com/app/docs/doc/817-2271/gbctt?l=ja&a=view --Tim
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