Am 18.03.2013 um 07:40 hat Wenchao Xia geschrieben: > δΊ 2013-3-15 22:51, Stefan Hajnoczi ει: > > On Fri, Mar 15, 2013 at 03:24:38PM +0800, Wenchao Xia wrote: > >> I'd like to add a new way to save vmstate, which will based on the > >> migration thread, but will write contents to block images, instead > >> of fd as stream. Following is the method to add API: > > > > Hi Wenchao, > > What use cases are there besides saving vmstate to a raw image? > > > > I'm curious if you're proposing this since there is no "file:" URI or > > because you really want to do things like saving vmstate into a qcow2 > > file or over NBD. > > > > Stefan > > > Hi, Stefan > Most used cases would be "raw" and "qcow2", which is flex and can be > chosen by user. In this way, existing block layer feature in qemu can > be used, such as tagging zeros. I haven't check the buffer/cache status > in qemu block layer, but if there is, it can also benefit. > User can specify "raw" or "qcow2" according to host configuration, If > there is dedicated storage components underlining, he can use "raw" to > skip qemu's block layer.
Oh, seems I misread this then. I thought this was about internal live snapshots, which is a feature that I consider really useful. I'm not so sure if saving the VM state as the disk contents of a qcow2 image is really helpful. If zero clusters help a lot, then there's clearly something to improve in the migration protocol, because it shouldn't send so many zeros in the first place. Kevin
