Re: [Xen-users] High availability and live migration with just LVMand hardware fencing

[Bart Coninckx <bart.coninckx@xxxxxxxxxx>]

On Thursday 20 May 2010 15:21:10 John Madden wrote:
> > I did some more thinking in regards to the snapshotting and came up with
> > the following: the backend storage is an IET storage target. I could
> > build the LUNs on top of LV's. This would give me snapshotting for the
> > Xen setup. Granted, not very elegant, since for a restore I need to put
> > the snapshot back and as a added action I need to connect to it from an
> > iSCSI initiator in order to access the data.
> 
> You'll have the same problems here as you will snapshotting from dom0 --
> filesystem cache and application state.  If the OS hasn't flushed its
> cache and frozen the filesystem, any snapshot from the block level would
> contain an inconsistent filesystem.  This is not an acceptable backup
> mechanism and I think doing it from IET (i.e., the SAN) is even worse
> because you have yet another layer of abstraction and potential for caches.
> 
> Note Jeff's note on SAN snapshots and gfs_tool.  His snapshots work
> because the OS is made aware of the need to flush caches and temporarily
> queue writes to the disk.
> 
> John
> 

Would a "xm suspend" before the snapstho not accomplish this? 

Cheers,

Bart

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users