openstack-create-qcow2-snapshot

openstack-create-qcow2-snapshot

In this example, an instance was launched with flavor 80G. installation didn't consume much of the disk. When snapshot was created without below steps its size was 80G (since openstack has raw in _base and snapshot creates with that raw size). By doing below (pull ing from _base to disk, qcow2 without the raw backing file reduces size of snapshot).

root@a6s15:/var/lib/nova/instances/ed719037-2e00-4c4c-90f9-924578f93b80# qemu-img info disk
image: disk
file format: qcow2
virtual size: 80G (85899345920 bytes)
disk size: 77M
cluster_size: 65536
** backing file: /var/lib/nova/instances/_base/1d043087def843d5e081c1e2c3ea6ca1e4278547 **
Format specific information:
    compat: 1.1
    lazy refcounts: false
root@a6s15:/var/lib/nova/instances/ed719037-2e00-4c4c-90f9-924578f93b80# virsh blockpull instance-00000140 vda --verbose --wait
Block Pull: [100 %]
Pull complete
root@a6s15:/var/lib/nova/instances/ed719037-2e00-4c4c-90f9-924578f93b80# qemu-img info disk
image: disk
file format: qcow2
virtual size: 80G (85899345920 bytes)
disk size: 3.1G
cluster_size: 65536
Format specific information:
    compat: 1.1
    lazy refcounts: false

Now you can create snapshot using openstack API and created snapshot will be small in size.