2010/3/31 Chris Lalancette <clalance@xxxxxxxxxx>: > On 03/30/2010 08:14 PM, Matthias Bolte wrote: >> 2010/3/30 Chris Lalancette <clalance@xxxxxxxxxx>: >>> Hello, >>> After our discussions about the snapshot API last week, I went ahead and implemented >>> quite a bit of the API. I also went back to the ESX, Virtualbox, and QEMU API's to >>> try and make sure our API's matched up. What's below is my revised API based on >>> that survey. Following my revised API are notes that I took regarding how the >>> libvirt API matches up to the various API's, and some questions about semantics that >>> I had while doing the survey. More comments and questions are welcome. >>> Mapping of our interface to various hypervisors: >>> +-------------------------------+-----------------+-------------------+------------------------------+ >>> | Libvirt | Qemu | Virtualbox | ESX | >>> +-------------------------------+-----------------+-------------------+------------------------------+ >>> | virDomainSnapshotCreateXML | monitor command | takeSnapshot | CreateSnapshot_task | >>> | | "savevm"; if | Snapshots can | takes a name, description, | >>> | | snapshot name | be taken on | memory (true/false) and | >>> | | is already in | powered off, | quiesce (true/false). | >>> | | use, replaces | saved, running, | What does "memory" mean? | >> >> If memory is true, ESX snapshots the memory of the domain too, >> otherwise only a disk snapshot is created. >> >> Creating a disk-only snapshot is nearly instant, while creating a >> memory snapshot also requires a notable amount of time to write the >> memory image to disk. > > Sorry, I misread the documentation yesterday. That's fairly clear. > What's less clear to me is what happens when you take a disk-only snapshot, > and then try to RevertToSnapshot from a running VM. What happens in that case? If the domain is running and you revert to a disk-only snapshot then the domain gets shutdown. Or rephrased: the power state associated with a disk-only snapshot is always powered-off, even if the domain was running while the disk-only snapshot was created. >> >>> | | the previous | or paused VMs. | Should we model "quiesce" | >> >> The vSphere API docs give a good description what the quiesce option does: >> >> "If TRUE and the virtual machine is powered on when the snapshot is >> taken, VMware Tools is used to quiesce the file system in the virtual >> machine. This assures that a disk snapshot represents a consistent >> state of the guest file systems. If the virtual machine is powered off >> or VMware Tools are not available, the quiesce flag is ignored." >> >> I assume "quiesce the file system" means to flush write caches and >> stuff like that. >> >> This option is important if you want to create a disk-only snapshot of >> a running domain. > > Exactly. I'm not sure this is going to be possible in general (and > I guess it's not even really possible in ESX unless you install VMware > Tools inside the guest). I'm inclined not to model it at the moment, > although I could be convinced otherwise. Yes, quiesce requires VMware Tools to be installed in the guest. Matthias -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list