On Sun, Jan 9, 2011 at 11:00 AM, Lentes, Bernd < [email protected]> wrote:
> Hi, > > Currently everything is clear. > Thanks for your help Yea I was out of pocket for a few days, but basically, you end up with 3 DRBD devices, 1 per VM/service right? When I said "dual-primary" I was speaking of DRBD only. DRBD in "dual-primary" aka "active-active" is analogous to a "shared storage"--such as a DAS or SAN connected to servers via HBAs with the same LUN mapped to both servers--modulo split-brain considerations as explained above. The reason you make it active-active on both nodes is because with Live-Migration the VM does exist simultaneously on both nodes for a brief period of time as the memory pages/state are migrated over and both access the block device simultaneously yet in a synchronized manner through the underlying HyperVisor. Indeed, there is a mechanism in place for synchronization as your surmised there must be. -JR
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