On 04/09/2014 15:02, Chris Wilson wrote:
Hi all,
On Thu, 4 Sep 2014, Dominic Raferd wrote:
If I had enough space for the LVM snapshot, I would probably rsync
the current
data and run rdiff-backup locally on the destination every time
rsync succeeds.
This would provide - in our setup - the same protection as LVM with
respect
to broken increments, but also resume a partial session after
network shortage
and server restarts.
You are facing quite a tough situation! You didn't comment on the
idea of lengthening the ssh timeouts, but given the severity of the
situations you have to allow for, maybe this can't help. I should
point out that using an LVM snapshot should not need nearly as much
space as rsync because it only has to store the differences between
the old rdiff-backup archive and the new, and it does not have to
persist once the backup is complete. Still rsync is a simpler (and
more familiar) solution and surely the lack of disk space is cheaper
to fix than the value of your time recoding rdiff-backup?
That gives me an interesting idea. Since the rdiff-backup destination
is a mirror of the source, we can rsync over it. Of course if we did
this on a real repository it would destroy it, but we could safely do
this:
* create a writable LVM snapshot containing the rdiff-backup repository,
* delete the rdiff-backup-data directory from it,
* rsync from the target over the snapshot's rdiff directory,
* run rdiff-backup from the snapshot back to the original location,
* then discard the snapshot.
Cheers, Chris.
I like that idea. But whereas the initial snapshot takes up almost no
disk space, I think that deleting its rdiff-backup-data directory would
cause it to swell in size by the size of the rdiff-backup-data
directory, or perhaps somewhat more (since snapshotting works at block
level). Better just to rsync to it ignoring the rdiff-backup-data
directory on the destination (I think using rsync --excl
/rdiff-backup-data should do it). Then, as you suggest, run rdiff-backup
from the snapshot back to the original location, again ignoring
/rdiff-backup-data on the source (rdiff-backup-data --exclude
/rdiff-backup-data) - or maybe rdiff-backup would ignore it anyway?
Cheers, Dominic
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