Re: [libvirt-users] Using virsh blockcopy -- what's it supposed to accomplish?

On 12/22/2014 03:27 PM, Gary R Hook wrote: > I am experimenting with the blockcopy command, and after figuring out > how to integrate qemu-nbd, nbd-client and > dumpxml/undefine/blockcopy/define/et. al. I have one remaining question: > > What's the point? Among other uses, live storage migration. Let's say you are running on a cluster, where your VM is running locally but was booted from network-accessed storage. You don't want any guest downtime, but you want to have the faster performance made possible by accessing local storage instead of the network-accessed storage. virsh blockcopy can be used to change qemu's notion of where the active layer of the disk lives without any guest time, by copying then pivoting to a local file.

> The "replication" disk file is not, from what I can ascertain, bootable. Correct in the current implementation, if you don't manually freeze guest I/O prior to the point where you abort the copy (whether you do a straight abort, leaving the copy as the point in time, or whether you do a pivot, leaving the original as the point in time). But I would like to add a --quiesce option to blockcopy, similar to what is already available for snapshot-create --quiesce.