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Re: [BackupPC-users] Block-level rsync-like hashing dd?
2011-04-12 15:51:33
Saturn2888 <backuppc-forum AT backupcentral DOT com> wrote
on 04/12/2011 12:11:49 AM:
> Les, that's a pretty good idea, running two, but I cannot do that
> with these systems sadly. It'd be really nice to not have to take
> the machine down to do the backup though. So I guess that's my
> question, I'm looking for a way to backup the pool over Ethernet
> while it's running.
If the pool is changing (as in, the filesystem is
mounted and BackupPC is running), then you *must* have some sort of snapshot
capability, and in any case, you're going to have to bounce BackupPC at
least *briefly*.
Therefore, you have two options: 1) LVM Snapshot/dd
or 2) Break a RAID mirror while unmounted.
> While it's possible to dd an lvm snapshot, that's
1TB/day which is
> quite a huge amount of time and bandwidth consumed. Is there no
> other solution like ddsnap?
Once you've got the LVM snapshot, you can do whatever
the heck you want to with it: any magic tool you wish for handling
the dd.
> I mean, since my BackupPC pool is on an
> lvm, doing a dd itself isn't the problem. It's that it's 1TB/day or
> more depending on my file system size. It'd be really nice to have
a
> solution to sync only the changes of that day which then, I can
> snapshot on the other machine. In my case, that other machine is the
> iSCSI target. I think DRBD is my best bet now, but it's more than
a
> handle to figure out; that's for sure.
With DRDB, you won't have to dd *ever*. BUT,
it won't help you in the case where something becomes corrupted (say, BackupPC
gets confused and deletes things): DRDB will *happily* corrupt both
copies. It's like RAID: RAID is not subsititue for backup.
There's no substitute for unconnected copies. DRDB
probably won't give you thtat.
Timothy J. Massey
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