Exactly. On Thu, Jun 7, 2018 at 10:21 AM, Terry hey <[email protected]> wrote:
> 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 <[email protected]>: > >> 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 <[email protected]> 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 -- [email protected] >>> To unsubscribe send an email to [email protected] >>> >>> >> >> >> -- >> Regards, >> Eyal Shenitzky >> > > -- Regards, Eyal Shenitzky
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