Hi 

I have a problem with the rsync incremental backups of a 50 GB binary
file. My set up consists of:
- Backuppc 3.2.1 running on Centos 5.7 with rsync 3.0.6. The server has
  2 GB of RAM with a single Xeon processor
- Client being backed up is Ubuntu Lucid server 
- Backup is done over a wireless link between 2 buildings which can
  provide for a 11 MB/s when tested with a plain rsync of a file
  between the 2 servers.
- The client receives a nightly copy of a ntbackup of a exchange 2003
  database to the /opt/samba/ntbackups folder. The file is
  currently around 51 GB in size

The problem I am having is that the incremental backups take around
double the time the full backups. These are the backuppc logs for full
backup following by a incremental on the next night:

Previous nights full:
2012-01-06 14:47:42 full backup started for directory / (baseline
backup #377)
2012-01-06 14:47:44 full backup started for directory /etc (baseline
backup #377)
2012-01-06 14:47:57 full backup started for directory /var (baseline
backup #377)
2012-01-06 14:50:49 full backup started for directory /opt (baseline
backup #377)
2012-01-06 18:38:38 full backup started for directory /root (baseline
backup #377)
2012-01-06 18:38:42 full backup started for directory /home (baseline
backup #377)
2012-01-06 19:02:59 full backup started for directory /usr (baseline
backup #377)
2012-01-06 19:07:07 full backup started for directory /bin (baseline
backup #377)
2012-01-06 19:07:10 full backup started for directory /sbin (baseline
backup #377)
2012-01-06 19:07:12 full backup started for directory /lib (baseline
backup #377)
2012-01-06 19:08:32 full backup 378 complete, 202077 files,
641375636764 bytes, 1 xferErrs (0 bad files, 0 bad shares, 1 other)

Last nights incremental
2012-01-07 15:00:10 incr backup started back to 2012-01-06 14:47:42
(backup #378) for directory /
2012-01-07 15:00:14 incr backup started back to 2012-01-06 14:47:42
(backup #378) for directory /etc
2012-01-07 15:00:21 incr backup started back to 2012-01-06 14:47:42
(backup #378) for directory /var
2012-01-07 15:03:39 incr backup started back to 2012-01-06 14:47:42
(backup #378) for directory /opt
2012-01-07 23:56:40 incr backup started back to 2012-01-06 14:47:42
(backup #378) for directory /root
2012-01-07 23:56:45 incr backup started back to 2012-01-06 14:47:42
(backup #378) for directory /home
2012-01-07 23:57:33 incr backup started back to 2012-01-06 14:47:42
(backup #378) for directory /usr
2012-01-07 23:59:42 incr backup started back to 2012-01-06 14:47:42
(backup #378) for directory /bin
2012-01-07 23:59:43 incr backup started back to 2012-01-06 14:47:42
(backup #378) for directory /sbin
2012-01-07 23:59:45 incr backup started back to 2012-01-06 14:47:42
(backup #378) for directory /lib
2012-01-08 00:00:26 incr backup 379 complete, 126 files, 55831250555
bytes, 0 xferErrs (0 bad files, 0 bad shares, 0 other)

You can see that the backup of the /opt share takes nearly the total
time of the incremental taking about 8 and half hours to complete while
the backup of the /opt rsync share in the full backup takes about 3 and
half hours. The full backup is slightly longer than what it takes if I
just do a rsync over ssh copy of the file from the client server to the
backup server. 

I have found that rsync seems to always transfer the whole file when
copying this file from the client server to the backup server:

# rsync -avzh --progress -e ssh
administrator@isabella:ExchangeDailyBackup.bkf ExchangeDailyBackup.bkf
Password:
receiving incremental file list
ExchangeDailyBackup.bkf
      54.44G 100%   10.66MB/s    1:21:10 (xfer#1, to-check=0/1)4

sent 3.31M bytes  received 3.27G bytes  486.33K bytes/sec
total size is 54.44G  speedup is 16.65.

My questions for the list are:
1. Is it reasonable for rsync to transfer the whole file when copying a
large ntbackup file? 
2. Why does an incremental backup of this file take so much longer than
a full backup of it or a plain rsync of this file?

Thank you

-- 
John Habermann
IT Officer
Cook Shire Council
10 Furneaux St
Cooktown 4895
ph 40820577

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