[ovirt-users] Re: Asking about snapshot concept

Hi Eyal, Thank you so much for answering me about snapshot concept. I am sorry for my late reply. Do you mean that when we create a new COW layer, we not only need to preserve the original disk, but we also need to mark the difference. Therefore, the disk format must be changed to be sparse? Also, what happen if we delete the snapshot. What we write in the new COW layer will be written into original layer? Regards Terry 2018-05-28 12:50 GMT+08:00 Eyal Shenitzky <eshenitz(a)redhat.com&gt;: > 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&gt; 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 >> >> _______________________________________________ >> Users mailing list -- users(a)ovirt.org >> To unsubscribe send an email to users-leave(a)ovirt.org >> >> > > > -- > Regards, > Eyal Shenitzky >