Thanks for this info. It was very helpful. I'm still trying to wrap my head around the scheduling and some of the terminology in the config.pl file.
-Rob Holger Parplies wrote: > Hi, > > Carl Wilhelm Soderstrom wrote on 09.07.2007 at 08:12:18 [Re: [BackupPC-users] > rsync incremental-only backups for eternity]: > >> On 07/09 08:22 , Rob Owens wrote: >> >>> I see that the only difference between rsync "full" and rsync >>> "incremental" backups is that "full" uses the --ignore-times option. >>> Under what circumstances would this option be desirable? Seems to me >>> that doing incremental backups forever would suffice, but maybe I'm >>> missing something. What is the risk associated with only performing >>> incremental backups with rsync? >>> > > http://sourceforge.net/mailarchive/message.php?msg_name=20070501024958.GM25826%40mail.parplies.de > http://sourceforge.net/mailarchive/message.php?msg_name=20070615011832.GL25826%40mail.parplies.de > > >> The way I tend to think of it (and I may be completely off base here) is >> that 'fulls' are like what you get if you just run the 'rsync' tool from the >> command line with no fancy options. 'Incrementals' are a faster way to do >> things. >> > > I believe 'rsync's default mode of operation is actually incremental-type > (i.e. optimize based on modification times). That makes sense for > interactive operation, as you can decide what you need each time. > '--ignore-times' is, in general, rarely needed, and it is an expensive > operation, much like '-H' (which is also not default, even in '-a'). If you > want to be absolutely sure you're making an exact copy, you need > 'rsync -aH --ignore-times', but usually 'rsync -a' will do (and be much > faster). Sometimes you might need to leave out '-o' and '-g' if you require > copies with identical content but different ownership. As always, you need > to know what you want before you can select the correct options to achieve > it. If your interactive invocation does *not* do what you expect, you'll > hopefully notice and correct it. > > For use as an automatic backup tool you want an invocation which produces an > exact copy of your data under all circumstances - for every machine, whatever > data your users happen to keep there, however they manipulate it. In addition, > you likely won't notice anything going wrong until you need to restore the > data > and the restored data is not correct. > > As backups are commonly done frequently and with large data sets, it may be > necessary to speed things up at an acceptable cost. Incremental backup > strategies based on modification times are common enough. The drawbacks are > basically known (if not always taken into account). With rsync, such a > strategy > *does* speed things up significantly, so it's natural to adopt a well known > term and its well known implementation, even though rsync "full" backups in > BackupPC already have almost all the benefits of conventional "incremental" > backups (storage and bandwidth wise). > > >> Always keep in mind tho that BackupPC is *not* using the rsync tool on the >> server side. It's using the File::RsyncP Perl module. >> > > Meaning not all options it respects are visible in the remote rsync > invocation, and not all rsync options are supported by File::RsyncP. > The '--delete' options are examples of things the remote instance does > not need to worry about. BackupPC will take note of deleted files > although these options are not explicitly visible. > > >> On 07/09 06:31 , Jean-Michel Beuken wrote: >> >>> in theory, in the version 3.x of BackupPC, we can take incrementals of >>> different levels ( $Conf{IncrLevels} )... >>> but, my little experience shows that we don't gain a lot of time with >>> high level (with rsync) worse some incr takes more >>> times that the full :-( >>> > > Some incrementals need to transfer more data than a full backup would in the > same situation :-). Note also the cost of constructing a backup view which > increases with the level of the backup. > > Regards, > Holger > > ------------------------------------------------------------------------- > This SF.net email is sponsored by DB2 Express > Download DB2 Express C - the FREE version of DB2 express and take > control of your XML. No limits. Just data. Click to get it now. > http://sourceforge.net/powerbar/db2/ > _______________________________________________ > BackupPC-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/backuppc-users > http://backuppc.sourceforge.net/ > ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ BackupPC-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/backuppc-users http://backuppc.sourceforge.net/
