On 2/24/11 9:34 PM, John Goerzen wrote:
>
> Next, I used mv to rename a file to a different name in the same
> directory and then ran another incremental.
>
> In this case, BackupPC noticed the file with the new name and backed it
> up.  It did not notice that the old file had gone away, which is
> somewhat as expected.  ls -lc confirmed that mv changed the ctime on the
> file.

If you rename a directory, you won't get the old contents underneath in their 
new locations either.  You'll still have the backup in the old path but might 
not know where to find it.

> Somewhat surprising was that rsync checksum caching provided only a
> marginal benefit (a reduction from 24.0 to 22.6 minutes for a full
> backup).  It is possible that the data set in question here (vast
> numbers of small files) is not good and displaying the benefit of
> checksum caching.

The client side still has to do a full read - probably mostly constrained by 
directory accesses and seeks on small files.

> The files in this test case did not demonstrate the other pathological
> problem with BackupPC's rsync algorithm, that of taking 10+ hours to
> back up a changed 25GB file.  Had such a file been involved, the tar
> backup would certainly have been many orders of magnitude faster than rsync.

You might do better with the --whole-file option on rsync if your server is 
slow 
doing the delta/merge operations.

>    * The rsync backend for BackupPC is probably not useful unless
> Internet backups or small backup sets to fast disks are involved.

That's perhaps an overstatement. But you do need relatively fast hardware on 
the 
server side.

>    * The "limitations" of the tar backend have been exaggerated, at least
> for backing up Linux systems with using POSIX-obeying filesystems with
> GNU tar.  (vfat under Linux may still exhibit the limitations
> documented, for instance.)

I think the docs combine the smb/tar description for this, and you would see 
the 
effect as described when using smb or tar on a client filesystem that doesn't 
support different mtime/ctime values.

> Does it point to any issues in BackupPC that are easily fixable?

Not unless someone wants to tackle what would have to change to not add the 
--ignore-times option on all full rsync runs.

-- 
    Les Mikesell
     lesmikesell AT gmail DOT com


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