Hi,
Francis Lessard wrote on 13.06.2007 at 13:13:13 [[BackupPC-users] Using Backup
PC in "online backup" model]:
> I currently use BackupPC 3.0.0 to backup 2 www servers. As bandwidth cost a
> lot, I would like to use BackupPC similar to a commercial online backup
> service we use. This service does a full backup only once, then do only
> incremental backups afterward. Am I correct if I set FullPeriod to 0, start
> a manual full backup, then let run incremental backup all the rest of the
> time ?
that would probably not do what you describe and certainly not what you
want. Incremental backups are relative to the previous backup of the next
lower level (meaning full backup in the simple case). You would be
transfering all changes since the full backup every time. Full backups are
done relative to the previous backup *of any level*. For a minimum of
bandwidth usage, you could do alternating full and incremental backups. You
could also experiment with multi-level incremental backups, but be aware
that with increasing level the costs to construct the view of the backup
increase, meaning running backups will get slower and slower, as will browsing
and restoring backups. That means you can't do level 365 backups, but you
can probably go to level 3 or 4 (but I'm just guessing, I haven't tried, and
it probably depends on your hardware).
> Hence, when there is a large volume of data on the initial full backup, the
> commercial service offers to send a physical disk to prevent bandwidth
> overuse. Is there any way to do this with BackupPC ? Using a locally
> connected device to fill the full backup, then let the incremental Rsync
> BackupPC do the rest ?
Yes, but it's not as simple as pressing a 'do initial backup from local
media' button. You'll have to trick BackupPC into thinking the first backup
(from a local machine) is from the same host as later backups (from the
remote machine). Look at $Conf{ClientNameAlias} and the list archive for
more details.
Francis Lessard wrote on 13.06.2007 at 21:13:01 [Re: [BackupPC-users] Using
Backup PC in "online backup" model]:
> [...]
> Each incremental backup takes around 4 minutes to do.
>
> [...] Usually, it takes about 20 seconds for a standard bash rsync script
> to update from the web server to a local backup backup directory.
The difference is probably due to the fact that BackupPC stores the files
compressed, so it needs to uncompress files with changed attributes where
plain rsync can simply read the file from disk.
If your BackupPC server is much slower than the client machine, the fact that
File::RsyncP is implemented in Perl might also make a difference.
Finally, there's the issue of seek times. With plain rsync, you might have
the file contents distributed in a way allowing faster access (on the backup
server) than is possible with file pooling (as they can only fit into one
backup file tree "naturally").
Les Mikesell wrote on 14.06.2007 at 10:07:13 [Re: [BackupPC-users] Using Backup
PC in "online backup" model]:
> The only other difference is that the full operation rebuilds a complete
> tree on the backuppc side that will be used as the base for subsequent
> incrementals.
This is important! You want to run a full backup regularly, not only for
minimizing bandwidth usage, but also for assuring your backups are correct.
Incremental backups are an optimization that may in rare cases miss things
(changed files with identical attributes, i.e. reset timestamps). The
speedup of the optimization is usually worthwhile, but you don't want to
rely on it indefinitely without making absolutely sure once in a while. That
is probably why BackupPC does not provide a convenient way to get by without
full backups.
Regards,
Holger
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