>
> The problem that you have to deal with is BackupPC's reliance on hard
links within the pool -- and this is supposedly dealt with in 4.x (?).
To resurrect some old discussions (
https://sourceforge.net/p/backuppc/mailman/message/27105491/):
> > * For most people, rsync does not work to replicate a backup server
> > effectively. Period. I think *no* one would suggest this as a reliable
> > ongoing method of replicating a BackupPC server. Ever.
> >
> > * The best methods for this boil down to two camps:
> > 1) Run two BackupPC servers and have both back up the hosts
> > directly
> > No replication at all: it just works.
> > 2) Use some sort of block-based method of replicating the data
> >
> > * Block-based replication boils down to two methods
> > 1) Use md or dm to create a RAID-1 array and rotate members of
> > this array in and out
> > 2) Use LVM to create snapshots of partitions and dd the partition
> > to a different drive
> > (I guess 3) Stop BackupPC long enough to do a dd of the partition
> > *without* lVM)
> >
> I think there is a 3rd camp:
> 3. Scripts that understand the special structure of the pool and pc
> trees and efficiently create lists of all hard links in pc
> directory.
> a] BackupPC_tarPCCOPY
> Included in standard BackupPC installations. It uses a perl
> script to recurse through the pc directory, calculate (and
> cache if you have enough memory) the file name md5sums and
> then uses that to create a tar-formatted file of the hard
> links that need to be created. This routine has been
> well-tested at least on smaller systems.
> b] BackupPC_copyPcPool
> Perl script that I recently wrote that should be significantly
> faster than [a], particularly on machines with low memory
> and/or slower cpus. This script creates a new temporary
> inode-number indexed pool to allow direct lookup of links and
> avoid having to calculate and check file name md5sums. The
> pool is then rsynced (without hard links -- i.e. no -H flag)
> and then the restore script is run to recreate the hard
> links. I recently used this to successfully copy over a pool of
> almost 1 million files and a pc tree of about 10 million files.
> See the recent archives to retrieve a copy.
Also,
http://backuppc.sourceforge.net/faq/limitations.html#some_tape_backup_systems_aren_t_smart_about_hard_links
:
Some tape backup systems aren't smart about hard links
> If you backup the BackupPC pool to tape you need to make sure that the
> tape backup system is smart about hard links. For example, if you simply
> try to tar the BackupPC pool to tape you will backup a lot more data than
> is necessary.
> Using the example at the start of the installation section, 65 hosts are
> backed up with each full backup averaging 3.2GB. Storing one full backup
> and two incremental backups per laptop is around 240GB of raw data. But
> because of the pooling of identical files, only 87GB is used (with
> compression the total is lower). If you run du or tar on the data
> directory, there will appear to be 240GB of data, plus the size of the pool
> (around 87GB), or 327GB total.
> If your tape backup system is not smart about hard links an alternative is
> to periodically backup just the last successful backup for each host to
> tape. Another alternative is to do a low-level dump of the pool file system
> (ie: /dev/hda1 or similar) using dump(1).
> Supporting more efficient tape backup is an area for further development.
I think that this answers your questions about tape requirements if
directly tar'ing the pool. You might be better off just scheduling host
archives periodically.
I don't know if Jeffrey Kosowsky still monitors the list, but somebody
might have a copy of his scripts (3b, above). Unfortunately, these were
part of the original BackupPC Wiki, which is no longer available.
Kris Lou
k...@themusiclink.net
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