Peter Walter wrote:

> What I don't understand is why such a great backup system such as 
> backuppc cannot reasonably be used to backup itself - it seems to me 
> that since backuppc "knows" it's own architecture, a way could be found 
> to do it efficiently.

Actually, backuppc doesn't know that much about what the filesystem is 
doing - for example, internally it never needs to know anything about 
'other' links except when initially creating them in the pool and when 
the count of links drops to 1.

> Since my objective is to do second-level disaster 
> recovery, allowing a day or two to restore a backuppc machine would work 
> for me - since the original hardware and the targets that were backed up 
> would have probably been destroyed in the disaster anyway, operations 
> may need to be moved to another site, etc. I think the locations within 
> which I have installed backuppc would be willing to wait for five days 
> for full functionality to be restored - meaning, the primary backup 
> machine being recreated, and the targets of the primary backup machine 
> being restored. Since, as I understand it, the hardlink usage in 
> backuppc is the primary reason why rsync cannot efficiently backup a 
> backuppc machine, I would be satisfied if the hardlinks were dumped 
> seperately, and a way to reconstitute them provided, with the pool(s) 
> being backed up as normal.

First you need to consider the scale you need to handle  For some size 
of archive (based more on number of files than size) and some amount of 
RAM and bandwidth, you can succeed with the obvious 'rsync -aH' of 
TOPDIR - perhaps making the initial snapshot at the primary location and 
moving it if you don't have the bandwidth for that part.  Rsync version 
3.x is much better than older versions.  There will still be a limit to 
what it can move in a practical amount of time but it might work in your 
situation.

> If a solution like that is not feasible, then I will have to consider 
> image copies of one sort or another of the primary backup servers. 
> However, there probably will be a limit to how many image copies could 
> be done in a day. With backuppc, as I understand it, the configurable 
> interval between incrementals and the pooling mechanism would allow me 
> to more or less continuously backup the primary backup servers.
> 
> If I have misunderstood anything about how backuppc could work in the 
> environment I suggest, please let me know.

Another approach would be to establish a VPN between your secondary and 
primary server,  give the secondary a route to the targets through it 
and let them run independently.   When you update the same file on many 
hosts, the secondary will have to copy all of them separately, but 
that's probably a rare situation and it avoids having the primary as a 
single point of failure that might be automatically propagated to your 
secondary copies.

-- 
   Les Mikesell
    lesmikesell AT gmail DOT com

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