[PVE-User] Backup size

[VIDAL, Thomas (Bioversity-France)]

Dear all,

I'm using Proxmox version 3.2-1, and since several weeks or months (but 
not before) backup of VMs take a long time and this is because the size 
of each VMs backup are biggest as before.

Before :
On a VM hosting debian server, with a VM disk size of 32G, and a system 
and datas size around 4G, the backup was fast and the size of the backup 
file was around 3G
Since several weeks :
The same VM with the same size of disk and datas take long time to 
backup and the size of the backup file is around 17G !

Could you point me on the right direction to solve this problem ?

Many thanks

Thomas