On Thu, Mar 31, 2011 at 09:59:43AM -0400, nhoeller AT sinet DOT ca wrote:
> I am running backuppc 3.1.0-4 on a plug computer (ARM processor) with the 
> Perl rsync fix for ARM processors.  On March 24, backuppc did an 
> incremental backup that picked up two 350MB files which had been uploaded 
> to my web server. On March,25, backuppc did a full backup and indicated 
> that the files were 'same' - data transfer was its normally low levels. 
> Subsequent incremental backups show no activity for these two files. 
> 
> I moved the two files to another directory on my web server sometime on 
> March 28.  The next incremental backuppc run early on March 29th showed a 
> backup of the two files in the new location (flagged as 'pool') followed 
> by a 'delete' of the files in the old location.  My backup bandwidth 
> jumped by over 700MB. 
> 
> The incremental backup early on March 30th showed the same results: 'pool' 
> for the files in the new location, 'delete' for the files in the old 
> location, 700MB of backup bandwidth.  I ran a full backup later on March 
> 30th.  This time, backuppc flagged the files as 'same' in the new 
> directory and nothing reported for the deleted files.
> 
> Two questions:
> * Why did the March 29th incremental backup not recognize that the files 
> were already in the backup pool?
> * Why did the March 30th incremental backup not recognize that the files 
> had been backed up from the new location?

What level were the two incremental backups? If both the march 29 and
march 30 backups were at the same level, they were using the last
backup at a higher (e.g. full) level as their baseline. With respect
to that baseline what you saw was correct. The files were moved, so
they were transferred across ino the new location (accounting for the
700 MB bandwidth increase) and marked deleted from the old location.

(Note that I think full backups use the last complete backup of any
level as their reference backup since the setting to ignore times
means every file will be compared and nothing will be skipped.)

Transfer decisions are based on the file names under the pc
directory. If the file doesn't exist in the comparison tree (which is
taken from the previous higher level backup for incrementals IIRC) it
is transferred. Different names/path result in the file being
transferred again.

Pooling decisions are based on the checksums of the files that were
transferred. Newly transferred files are checksummed and compared to
files in the pool. So after the transfer occurred pooling should have
happened and those newly transferred files would have been hardlinked
into the pooled file.

Files that exist in the comparison/reference tree and that are the
same as the files on the remote system (i.e. there were no delta
transfers for the file by rsync) aren't touched and are shown as same.

The only way the March 30'th backup wouldn't have transferred the
files was if the march 29th backup was a level 1 incremental and the
march 30'th was a level 2 incremental. In that casse the march 30'th
incrmentals reference tree would have been from the march 29 backup
which already had the files in the new (moved) location and it would
have been able to determine that the files were identical.

-- 
                                -- rouilj

John Rouillard       System Administrator
Renesys Corporation  603-244-9084 (cell)  603-643-9300 x 111

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