On Wed, Jan 20, 2010 at 09:15:48PM +0200, Pasi Kärkkäinen wrote: > On Wed, Jan 20, 2010 at 03:14:02PM +0100, Dirk H. Schulz wrote: > > Pasi Kärkkäinen schrieb: > >> On Sun, Jan 17, 2010 at 02:47:00PM +0100, Dirk H. Schulz wrote: > >> > >>> Ray Van Dolson schrieb: > >>> > >>>>> Hmm.. so snapshots with CLVM are possible nowadays? > >>>>> > >>>> No.... > >>>> > >>>> RH has stated (recently on this list) that patches exist to do it, but > >>>> it hasn't been a high enough priority for them to complete the work to > >>>> the point where it could be distributed to customers. > >>>> > >>> Okay then, how do you people out there with clusters that run virtual > >>> machines with live migration do backups of the virtual machines? > >>> I surely do not want to shut down the virtual machine to be able to > >>> copy the image safely away if I have live migration available. > >>> > >>> At the moment there is only one way I can see. PLEASE prove me to be wrong. > >>> Searching in RedHat's documentation I found that the problem is that > >>> lvm snapshots need exclusively allocated logical volumes. So I think > >>> the following > >>> should be technically possible: > >>> 0. Start environment: the logical volume containing the images of the > >>> virtual machines uses gfs and is mounted on all relevant cluster > >>> nodes since VMs are running on several cluster nodes. > >>> 1. All VMs have to be migrated to one of the cluster nodes > >>> 2. On all other nodes, the gfs volume is unmounted > >>> 3. On the remaining node (where all VMs now run) the logical volume > >>> is bound exclusively with "lvchange -aey LOGICALVOLUME" > >>> (I hope this is possible without deactivating it first) > >>> 4. Now GFS on this volume is frozen: "gfs_tool freeze > >>> /mountpoint/of/local/volume" > >>> > >> > >> Before freezing the GFS you should make sure the VMs are in consistent > >> state, and the VMs have flushed their caches/buffers/disks. > >> > > That means calling sync > > echo 3 > /proc/sys/vm/drop_caches > > inside the VM, right? Or is there anything more to do to flush everything? > > > > And before those commands stop any databases or complex applications.. > or make them flush their buffers and lock the tables for writes. > You might also be interested of this thread: http://lists.xensource.com/archives/html/xen-users/2010-01/msg00393.html -- Pasi -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
