Am 16.06.25 um 13:07 schrieb DERUMIER, Alexandre via pve-devel: >>> The 'snapshot' option, for QEMU's snapshot mode, i.e. writes are only >>> temporary, is not yet supported. > > from qemu manpage: > > " > -snapshot > Write to temporary files instead of disk image files. In > this case, the raw disk image you use is not written back. You can > however force the write back by pressing C-a s (see the Disk Images > chapter in the System Emulation Users Guide). > > WARNING: > snapshot is incompatible with -blockdev (instead use > qemu-img to manually create snapshot images to attach to your > blockdev). If you have mixed -blockdev and -drive declarations you can > use the 'snapshot' property on your drive declarations instead of this > global > option. > " > > So, if we want to keep this option. (I never used it to be honest),
I've briefly talked with Fabian about this a while ago. Yes, we do want to keep it and it will be useful for https://bugzilla.proxmox.com/show_bug.cgi?id=5187#c3 > I think we should create a temporary qcow2 file at vm start and delete > it at vm stop. Yes, we need an overlay. Note that there already is a FIXME comment too ;) >> + # FIXME use overlay and new config option to define storage for temp >> write device >> + die "'snapshot' option is not yet supported for '-blockdev'\n" if >> $drive->{snapshot}; > I'm not sure of current behaviour when you use a block device ? Note that what you linked above is for the global '-snapshot' option, not the drive one. It just doesn't apply to blockdevs AFAIU. > how qemu known where to write a temp snapshot file ? It just uses /var/tmp which of course is not ideal. > maybe we could reuse state storage ? only with a temp qcow2 file ? or > do we want to reuse snapshot feature of storage ? We want to add a dedicated option to select a snapshot storage. There could be a sensible default selection (depending on restrictions for the overlay image). > Also, I think that some features should be disable when it's used. > (vm snapshots for example, maybe move disk,...) Haven't looked into that, but would be pre-existing issues, so nothing urgent. We just shouldn't break the feature if not necessary. If we really don't get around to support it in time for PVE 9 we could also initially note it as a breaking change or fallback to -drive. _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
