kvm qcow snapshot

[informant]

Hi all,

if i make a snapshot of a qcow vm, is it a file on harddisc, if yes where i can find it, how many space use it and how can i set a limit and where can i configure the save path? Or is it only a restore point without using backupspace? what is, if i have configure 0 backups, can i create snapshots?

I hope you can help me, thanks and regards

 

[spirit]

Hi, snapshots are internal in the disk qcow2 file.
It don't use space at the moment of the snapshot. But new writes after snasphot take space.
(If you rewrite the full disk after a snasphot, you'll have a file twice bigger.

(backups are not related to snasphots)

 

[informant]

Hi, thansk for your answer. a snapshot used also the space of vm file and not other. thanks and happy new yearr

regards

 

[blackpaw]

Live snapshots of a running vm will create a external file to store the ram and machine state. This is stored in the same directory as the virtual hd.

Sent from my MT27i using Tapatalk

 

[mir]

On the contrary. The original image is converted to raw and any further write to the image is done to a new file in qcow2 format.
file vm-140-state-clean.raw
vm-140-state-clean.raw: QEMU suspend to disk image
file vm-140-disk-1.qcow2
vm-140-disk-1.qcow2: QEMU QCOW Image (v2), 6442450944 bytes

 

[blackpaw]

On the contrary. The original image is converted to raw and any further write to the image is done to a new file in qcow2 format.

Eh? not sure what you mean - not seeing this at all. On my nfs qcow2 vm, disk only snapshot are nearly instant and are stored internal on the qcow2 disk. Nothing is converted to raw.

 

[aderumier]

Eh? not sure what you mean - not seeing this at all. On my nfs qcow2 vm, disk only snapshot are nearly instant and are stored internal on the qcow2 disk. Nothing is converted to raw.

The external raw file is only to save the vm state (memory), if you want to rollback to a running vm. but it's optionnal.
Disk data snasphot is internal in the qcow2 file.

 

[blackpaw]

Ah, that makes more sense.

 

[informant]

Nice informations. But can i configure a max of snapshots, if yes, where?

regards