On 20/11/2014 06:36, 정복득 wrote: > Hi, > > I have a question about block commit and internal vm snapshot. > > I am using an overlay file to run a virtual machine. > I took a snapshot with the 'vmsave' qemu monitor command, then commited > blocks in the overlay file into the backing file after playing with my > virtual machine a while and then shutting down it. > Because every block in the overlay file merged to the backing file, I deleted > the overlay file. > After I started virtual machine with the backing file later on, I checked the > snapshot with 'info snapshots' at qemu monitor but couldn't see any snapshots > at all. Meanwhile, block commit seemed successful as I could see files that I > added while the VM was using the overlay file. > > Internal snapshots with vmstate in an overlay file are not merged to the > backing file? > What should I do if I want to preserve internal snapshots into the backing > file? > Is there a way that I can take a external snapshot? I am not using libvirt or > virsh.
vmsave memory snapshots can only be stored in qcow2 files. If you somehow set up one qcow2 file to use another qcow2 file as its backing store, I don't think there is any command to transfer snapshots (disk or memory) from the overlay qcow2 to the backing qcow2 and stillappear as snapshots in the backing qcow2. When creating an internal snapshot in an existing qcow2 backing file, there is some vagueness in the documentation as to where the saved memory is stored in the qcow2 file structure: In the frozen snapshot or in the internal overlay. If the vmsave memory/register image is stored in the part of the qcow2 file which represents the disk contents at snapshot time, it would be an interesting issue to look at the ability to commit this part to a qcow2 backing store when committing the block changes in a non-running snapshot to that same qcow2 backing store. However in your case it sounds like you committed the "running" disk blocks to the backing store, essentially removing the snapshot (and making any references to disk contents in the vmsave memory snapshot invalid anyway). Enjoy Jakob -- Jakob Bohm, CIO, Partner, WiseMo A/S. http://www.wisemo.com Transformervej 29, 2860 Søborg, Denmark. Direct +45 31 13 16 10 This public discussion message is non-binding and may contain errors. WiseMo - Remote Service Management for PCs, Phones and Embedded
