Actual disk usage and vzdump size is way different

[Bivas Mandal]

Hello,

Not sure if this is correct behavior.

VM 101
Assigned disk

$ sudo qm config 101 | grep ^scsi0
scsi0: data:101/vm-101-disk-1.qcow2,size=53452M

Actual disk usage

Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1        51G   20G   32G  38% /

vzdump size

28G    vzdump-qemu-101-2018_09_26-13_30_02.vma.lzo

+++++++++++++++++++++++++++++++++++++++++++++++

VM 105
Assigned disk

$ sudo qm config 105 | grep ^scsi0
scsi0: data:105/vm-105-disk-1.qcow2,size=27852M

Actual disk usage

Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1        27G   19G  7.5G  72% /

vzdump size

9.3G    vzdump-qemu-105-2018_09_26-13_45_13.vma.lzo

If you notice closely, the vzdump size is less then actual disk usage for VM 105, which is not the case with VM 101

Both VM is pretty much identical in term of configuration
Ubuntu Cloud image 16.04
pve-manager 5.2-1

Any input would be greatly appreciated.

 

[dcsapak]

this depends greatly on the data, since both backups are compressed (note the '.lzo' ending) with LZO
so if your data is easy to compress, the image will be smaller

on the other hand, if your vm writes many/big files and deletes them afterwards (and does not trigger an fstrim) the blocks on the disk still look like they are used, so they will be backed up