On an instance of the NetApp Simulator, I was able to take a snapshot, export it via NFS, create a loopback device based on the snapshot, and mount the filesystem within it; something like:
Filer> lun create -b /vol/vol1/luns/lun11 -o noreserve /vol/vol1/luns/lun11_snapforback
Filer> lun share /vol/vol1/luns/lun11_snapforback read
Linux> mount 10.10.10.23:/vol/vol1 /mnt/netapp-vol1
Linux> losetup -f /mnt/nasim9-vol1/luns/lun11_snapforback
Linux> kpartx -a /dev/loop1
Linux> mount /dev/loop1p5 /mnt/lun11-snap
However, as I said, we don't have an NFS license; we've also heard that NFS performance is poorer than iSCSI performance. My guess is that some commands like the following ought to work:
Filer> lun map /vol/vol1/luns/lun11_snapforback linux-host 3
Linux> iscsiadm -m discovery --interface eth0 -t st -p 10.10.10.23 --login
Linux> iscsiadm -m node --interface eth0 -p 10.10.10.23 --login
Linux> mount /dev/sde /mnt/lun11-snap
When I do that, though, the set of available SCSI disk devices on the Linux host doesn't change. Perhaps this is an open-iscsi limitation instead?
To answer Jack's questions:
We had Bacula working on the backup-host, and it doesn't support NDMP. I don't think that would be any use for a LUN (which is just an opaque file to the NetApp), anyway.
Yes, we do want to avoid the overhead of the backup job on the host, and traffic across two network links when only one should be necessary. We also want to make as few software changes on the other hosts as possible.
We don't have a FlexClone license.
--
David Lee Lambert
Software Developer, Precision Motor Transport Group, LLC
517-349-3011 x223 (work) ... 586-873-8813 (cell)
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From: Romeo Theriault [mailto:romeotheriault@gmail.com] Sent: Wednesday, November 12, 2008 10:11 AM To: David L. Lambert; Toasters Subject: Re: Mounting read-only snapshots using open-iscsi?
I'm not 100% sure of this, but I don't think you can map and mount a snapshot itself. (I may be wrong, someone please let me know if I am) but I believe that you'll need a flexclone license to create a clone of that particular snapshot and then map the clone to your backup host.
On Wed, Nov 12, 2008 at 8:41 AM, David L. Lambert dlambert@bmtcarhaul.com wrote:
[...]
We also have an Ubuntu system connected to a tape library. We would like to take snapshots of the data-volumes that need to be backed up, mount those snapshots on the backup host, and do an incremental backup from the mounted filesystem.
Probably we would partition each LUN with one Linux partition, and put an ext3 or reiserfs filesystem with a cluster-unique label on that partition. Then we could take a set of snapshots for the backup, map all the snapshot LUNs to the backup-host, do iSCSI discovery on the backup-host, mount each partition (listed in a configuration-file) with a "mount LABEL=..." command, perform the backup, unmount the partition, do an iSCSI logout, and delete all the snapshots.