Rsync of LVM Snapshots copies whole file

[Mac User FR]

The problem with disk image as databases is that data change a lot  
into the file.
When you run a system on a disk image, thre is not only new data  
appending to the end of the file, but the entire disk image is changing.
Same thing would happen with large Outlook .pst databases.
Rsync nor any other partial data transfer could deal with it as those  
files are "black boxes" seen from the backup tool. They only make  
sense from inside the program that create them.
The best way to solve this problem is to not do the backup of the disk  
image, but backup from the system inside the disk image. Then, rsync  
can see file changes easily.

Best regards,

Vitorio

Le 15 août 08 à 20:41, Peter P GMX a écrit :

> Hello, anybody has a clue why this happens?
>
> The scenario:
> Each night I create LVM snapshot of my volume which contains some  
> virtual disk images (VirtualBox VDIs). Then I rsync the content of  
> one of the snapshot directories to a backup server. Each file size  
> is between 1.3 GB and 6GB.
> I run the following commmand:
> sudo -u rsyncbackup rsync -avzP --exclude-from /home/rsyncbackup/ 
> excludefile -e ssh "192.168.0.3:/mnt/vdi_snapshot/VDI/mit_backup" "/ 
> mnt/crypteddevice/linuxX2/mit_backup"
> The source directory is part of the LVM snapshot.
> The destination directory is a truecrypt device which is already  
> mounted.
>
> What I would expect:
> Only the differences of the virtual disk files should be transfered.
>
> What happens:
> I discover that always the whole file is transfered. Even if the  
> original virtual machine is idle (so only some log files should have  
> been enhaned in the virtual disk images).
> I do the following:
> - take LVM snapshot
> - Rsync the desired VDI file (2GB are transferred), it takes 10min
> - destroy LVM snapshot
> - take new LVM snapshot with same parameters as before
> - Rsync the same file (2GB are transferred), it takes 10min
>
> Am I doing something wrong?
>
> Best regards
> Peter
>
>
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