Errol Neal wrote:
Quoting Pierre-Alain RIVIERE <[EMAIL PROTECTED]>:
Hi,
I'm a pretty new user of Openfiler and I'm wondering myself what is the
best way to achieve iSCSI backup.
Indeed, I'm using iSCSI volume to export Xen block devices over
network. Each of my Xen DomU have its own iSCSI volume. On my Openfiler
box I have a LTO-3 tape drive and I want to make backup and recovery as
simple as possible.
I'm thinking about this procedure :
- make a LVM snapshot of my iSCSI volume
- dd the snapshot to a backup file (may be is it possible to pipe it
directly to the tape drive?)
- send the backup to the tape drive
- delete the LVM snapshot
And in case of disaster I should have only to restore LVM metadata and
write backup to LVM volume using dd.
What do you think about this usage? Am I wrong somewhere? May be I
missed something?
It's not going to be possible to pipe a snap directly to tape because
a snapshot doesn't involve any "data", only information about where
the data is.
You should be able to dd the volume, you may be able to pipe it to
tape from dd, but I wouldn't recommend that because dd isn't smart
enough in this regard.
What I do is actually mount the volume and back it up using Backup
Exec. In your case, you can use tar to write it to tape.
I'd really prefer to avoid mounting the volume before backing it up. And
in the case I should proceed the way you describe, there's something I
missed about LVM volumes I think.
I've just proceed some tests: create a snapshot of a LVM volume and try
to back it up after mounting the volume. But then, I don't understand
how to proceed to mount my partitions. I think my LVM snapshot volume is
OK as I can use fdisk on it to list the disk partitions
# fdisk -l /dev/XenDomains/of.snapshot.ares.bac
Disk /dev/XenDomains/of.snapshot.ares.ippon.fr.bac: 7851 MB, 7851737088
bytes
242 heads, 62 sectors/track, 1022 cylinders
Units = cylinders of 15004 * 512 = 7682048 bytes
Device Boot Start
End Blocks Id System
/dev/XenDomains/of.snapshot.ares.bac1 * 1 781
5859031 83 Linux
/dev/XenDomains/of.snapshot.ares.bac2 782 848
502634 83 Linux
/dev/XenDomains/of.snapshot.ares.bac3 849 981
997766 83 Linux
/dev/XenDomains/of.snapshot.ares.bac4 982 1022
307582 82 Linux swap / Solaris
But when I want to mount the partitions (here there's 3 partitions to be
back up), I don't know which device to use.
/dev/XenDomains/of.snapshot.ares.bac is a disk and I don't find the
devices for the disk partitions (/dev/XenDomains/of.snapshot.ares.bac#
do not exist).
What did I miss?
I must really export the snapshot via iSCSI before being able to mount
its partitions?
Also, its just my recommendation, but I'd suggest not exporting a new
volume for each domU. I plan ahead and export all the data I need and
create volumes on the dom0. I think this reduces the load on both
your iscsi server and it's initiators.
Let's me clarify just to be sure I understand. You suggest to export one
big SCSI volume and attach it to the dom0. And then use LVM on the dom0
to create logical volumes for domU.
I'm OK with this solution - it's easier to implement and as you said
reduces the load on the servers -, but I have several dom0 and wish them
to have the capability to make live migration. In this case I should
also use CLVM to propagate LVM metadata modification, no?
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