Backing up a restore doubled rdiff-backup size

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Backing up a restore doubled rdiff-backup size

Blair Zajac
I use rdiff-backup to backup my wife's PowerBook's /Users/* directories and this
weekend I upgraded it from 10.3 to 10.4 by doing the following steps:

1) Attach external Firewire drive.
2) Clone internal disk to external using Carbon Copy Cloner.
3) Wipe internal disk.
4) Install 10.4.
5) Drag and drop directories from external disk back into internal disk.

I tried a test on my Ubuntu box doing something like this, with the contents the
same but the inode is different.  Rdiff-backup did a backup with no size change.

$ mkdir test
$ cp -p /etc/passwd test/
$ rdiff-backup test backup
$ cp -p /etc/passwd test/passwd1
$ mv test/passwd1 test/passwd
$ rdiff-backup test backup

So I was surprised when I got this report today.  I would assume that the diffs
would be 0 size, so the incremental size of the repository would be very small,
not almost a doubling of the size.

$ rdiff-backup --null-separator -v 5 --list-increment-sizes ashley-powerbook
ACLs not supported by filesystem at
/var/rdiff-backups/ashley-powerbook/rdiff-backup-data
-----------------------------------------------------------------
Detected abilities for /var/rdiff-backups/ashley-powerbook/rdiff-backup-data
(read only) file system:
   Access control lists                         Off
   Extended attributes                          On
   Case sensitivity                             On
   Mac OS X style resource forks                Off
   Mac OS X Finder information                  Off
-----------------------------------------------------------------
         Time                       Size        Cumulative size
-----------------------------------------------------------------------------
Sun Dec 18 22:48:07 2005         23.1 GB           23.1 GB   (current mirror)
Fri Dec 16 23:22:58 2005         21.6 GB           44.7 GB
Fri Dec 16 21:38:22 2005         6.54 MB           44.7 GB
Fri Dec 16 01:13:08 2005          197 MB           44.9 GB
Wed Dec 14 23:53:09 2005         61.1 MB           45.0 GB
Wed Dec 14 00:32:55 2005         6.49 MB           45.0 GB
Mon Dec 12 23:20:54 2005         25.2 MB           45.0 GB
Sun Dec 11 00:24:42 2005          458 MB           45.5 GB
Fri Dec  9 23:22:17 2005         16.9 MB           45.5 GB
Fri Dec  9 07:15:34 2005         8.70 MB           45.5 GB
Wed Dec  7 23:33:40 2005          162 MB           45.6 GB
Tue Dec  6 23:15:44 2005          290 MB           45.9 GB
Mon Dec  5 00:04:17 2005         1.12 GB           47.0 GB
Sun Dec  4 00:30:57 2005          210 MB           47.3 GB
Sat Dec  3 01:18:54 2005         68.1 MB           47.3 GB
Thu Dec  1 23:05:32 2005         22.9 MB           47.3 GB
Thu Dec  1 08:04:57 2005         9.17 MB           47.4 GB

$ cat session_statistics.2005-12-18T22:48:07-08:00.data
StartTime 1134974887.00 (Sun Dec 18 22:48:07 2005)
EndTime 1135021621.73 (Mon Dec 19 11:47:01 2005)
ElapsedTime 46734.57 (12 hours 58 minutes 54.57 seconds)
SourceFiles 71151
SourceFileSize 24738960103 (23.0 GB)
MirrorFiles 78164
MirrorFileSize 55819067916 (52.0 GB)
NewFiles 14191
NewFileSize 934670526 (891 MB)
DeletedFiles 21204
DeletedFileSize 31778439883 (29.6 GB)
ChangedFiles 56575
ChangedSourceSize 23804289577 (22.2 GB)
ChangedMirrorSize 24040628033 (22.4 GB)
IncrementFiles 91970
IncrementFileSize 23232724461 (21.6 GB)
TotalDestinationSizeChange -7847383352 (-7.31 GB)
Errors 0

I didn't restore a lof of the data that applications leave around, such as
browser cache files and the like, so I can see the -7.31 GB, but seeing
everything as changed is odd.

Or am I just mis-reading the information here?

Regards,
Blair

--
Blair Zajac, Ph.D.
<[hidden email]>
Subversion and Orca training and consulting
http://www.orcaware.com/svn/


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Re: Backing up a restore doubled rdiff-backup size

Ben Escoto
>>>>> Blair Zajac <[hidden email]>

>>>>> wrote the following on Mon, 19 Dec 2005 23:00:42 -0800
> I use rdiff-backup to backup my wife's PowerBook's /Users/*
> directories and this weekend I upgraded it from 10.3 to 10.4 by
> doing the following steps:
>
> 1) Attach external Firewire drive.
> 2) Clone internal disk to external using Carbon Copy Cloner.
> 3) Wipe internal disk.
> 4) Install 10.4.
> 5) Drag and drop directories from external disk back into internal disk.
...
>
> So I was surprised when I got this report today.  I would assume
> that the diffs would be 0 size, so the incremental size of the
> repository would be very small, not almost a doubling of the size.
...

> $ cat session_statistics.2005-12-18T22:48:07-08:00.data
> StartTime 1134974887.00 (Sun Dec 18 22:48:07 2005)
> EndTime 1135021621.73 (Mon Dec 19 11:47:01 2005)
> ElapsedTime 46734.57 (12 hours 58 minutes 54.57 seconds)
> SourceFiles 71151
> SourceFileSize 24738960103 (23.0 GB)
> MirrorFiles 78164
> MirrorFileSize 55819067916 (52.0 GB)
> NewFiles 14191
> NewFileSize 934670526 (891 MB)
> DeletedFiles 21204
> DeletedFileSize 31778439883 (29.6 GB)
> ChangedFiles 56575
> ChangedSourceSize 23804289577 (22.2 GB)
> ChangedMirrorSize 24040628033 (22.4 GB)
> IncrementFiles 91970
> IncrementFileSize 23232724461 (21.6 GB)
> TotalDestinationSizeChange -7847383352 (-7.31 GB)
> Errors 0
>
> I didn't restore a lof of the data that applications leave around,
> such as browser cache files and the like, so I can see the -7.31 GB,
> but seeing everything as changed is odd.
>
> Or am I just mis-reading the information here?
I think the session statistics jive with what you expected.  The
-7.31GB is the net change in the repository.  So after your backup,
the repository 7GB was smaller than when you started.

Since the new version of your directory is only 23GB (compared to 52GB
before), of course a lot of the repository will be dedicated to
storing all those files which no longer exist.  So if you deleted the
information on all those old files, the repository would be only half
as big.  That doesn't mean the size of the repository ever doubled.


--
Ben Escoto

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