Thank you Stefan! Now I understand the workflow. -Yaodong
On Fri, Jan 30, 2015 at 2:37 PM, Stefan Hajnoczi <stefa...@gmail.com> wrote: > On Fri, Jan 30, 2015 at 8:13 PM, Yaodong Yang <yaodong.ya...@gmail.com> > wrote: > > An follow up questions. > > > > Suppose I have a running VM with two virtual disks, I would like to > migrate > > the vm from host A to host B. Both host A and host B have their own > isolated > > storage devices. Is there anyway to migrate the vm's memory, two virtual > > disk images and other states together from host A to host B? Can > > drive_mirror command itself finish this job? I noticed that drive_mirror > > only mirror for one virtual disk and require both the source and > destination > > share the same storage namespace. I do not know how to migrate the whole > VM > > (memory, storage, network ) together from host A to host B, given that > host > > A and host B have NO shared storage resource. > > > > Could you show me an example, if possible? > > > > I know "migrate -b" works well for this purpose. But the downside is > > "migrate -b" does not mirror Write Requests to both host A and host B > during > > migration. In this case, "migrate -b" has a higher VM downtime during the > > migration. > > Hi Yaodong, > The answers to these questions are in libvirt's source code. It > orchestrates live migration between two hosts. > > Multiple independent drive_mirror jobs can run. That's how you handle > multiple disks. > > The regular migrate command (without -b) can be used if drive_mirror > is in place and fully synced. > > Libvirt sets up an NBD server on the destination host. The source > host runs drive_mirror to copy over the contents of the disk images. > Once the drive_mirror command has completed syncing data the regular > 'migrate' command can be used to send device state and RAM over to the > destination host. > > See qemuMigrationDriveMirror() in libvirt. > > migrate -b is a legacy feature that is being replaced by drive_mirror. > > Stefan > -- Yaodong Yang yaodong.ya...@gmail.com or yy...@cse.unl.edu Computer Science and Engineering Department University of Nebraska-Lincoln Lincoln, NE, USA
