Hey Terry,
When creating a snapshot it causes a new COW layer to be created over the
current layer.
All write actions performed after a snapshot is taken are written to the
new COW layer.
The format that supports the option of "growable" disks is sparse,
therefore, when creating a snapshot of the disk, the format must support
the option to add another layer and maintain the difference between them.
Regard to the snapshot size, it should contain all the changes between
the "old" disk layer (the snapshot) and the new layer (active snapshot) and
in order to achieve that, we should be able to mark each diff (note that
this is a qcow2 disk and not all the space is allocated).
You can look and search for another information here -
https://www.ovirt.org/documentation/admin-guide/
On Mon, May 28, 2018 at 6:21 AM, Terry hey <recreationh(a)gmail.com> wrote:
Dear all,
I have a pre-allocated virtual machine.
When i created a snapshot for that virtual machine, i found that it became
thin-provision.
And the size of the snapshot is same as the virtual machine.
i would like to ask why these two behavior happened.
1. preallocated to thin provision
2. the size of snapshot is same as the disk size of virtual machine.
Regards
Terry
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Regards,
Eyal Shenitzky