[SOLVED] About VM backup size

[samontetro]

I had a large Centos VM (32Gb) and to reduce the size of the backup I add a disk on my ceph storage with backup set to 0 (I toggle the no backup button and use a remote backuppc server for this area) and move all the data to this new storage (/dev/vdb). It remain less than 3GB on /dev/vda.

But Backup is still very large: 27GB with lzo compression and I do not understand why.

Patrick

/ and /boot on /dev/vda
/AUTOINSTALL on /dev/vdb
Using PVE 4.2

Filesystem                Size  Used Avail Use% Mounted on
/dev/mapper/cl_gaia-root   29G  2.7G   27G  10% /
/dev/vda1                1014M  232M  783M  23% /boot
/dev/vdb                   32G   31G  1.8G  95% /AUTOINSTALL

 

[wolfgang]

Hi,

On what storage backed the vda is?
And what format has the image?

If it is a thin allocated image you have to trim it in the VM.

 

[samontetro]

Hi Wolfgang,

The /dev/vda is on a ceph storage.
The backup is stored on a local hard drive partition on the node
It is not thin allocated image.

Today I had a idea: if backup is based on dd or dump commands, disks blocks, even not used, may still contain the erased data and compression will be ineficient.
I filled the disk with a file containing only zeros with

dd if=/dev/zero of=/home/zeros bs=1G count=25

then remove this file and launch a new backup.
It is only 3.3Gb now.

Patrick