In our ONE installation, while I expect snapshots to take space only when the base image file is modified, they actually take the full space of the base image from snapshot creation time.
This wastes both time and disk space, and defeats the whole purpose of using QCOW2 images over RAW images.
Well, Copy On Write should only copy … when you write
Any clues what in my settings is causing that ?
$ oneimage show 432 IMAGE 432 INFORMATION ID : 432 NAME : img-XXX-01N USER : oneadmin GROUP : oneadmin DATASTORE : DSXXX TYPE : DATABLOCK REGISTER TIME : 03/28 00:14:26 PERSISTENT : Yes SOURCE : /var/lib/one/datastores/105/IIIIIIIII FSTYPE : qcow2 SIZE : 20G STATE : used RUNNING_VMS : 1 PERMISSIONS OWNER : um- GROUP : --- OTHER : --- IMAGE SNAPSHOTS AC ID PARENT DATE SIZE NAME => 0 -1 03/31 06:53:50 20G SSSSSSSS\ IMAGE TEMPLATE DEV_PREFIX="vd" DRIVER="qcow2" VIRTUAL MACHINES ID USER GROUP NAME STAT UCPU UMEM HOST TIME 3992 oneadmin oneadmin VVVVVVVVVV runn 2.82 6G NNN-r999-0 5d 18h37 $
Both the image file :
and the snapshot file :
have equal (du) size at 21 GB.
Possible causes I can think of, appreciate any guidance where it could go wrong :
- Because I use NFS Shared datastore type which does not support QCOW2 image snapshot COW format ?
- Because my version is too old (OpenNebula 5.2.1) , the bug was fixed already ?
- Because the bug/feature is still there ?
- Because I use the wrong (default) settings for KVM cache=writethrough/none (see Snapshot issue) ?
Appreciate any suggestions how to fix this.