On Sun, Jan 9, 2011 at 11:00 AM, Lentes, Bernd <span dir="ltr"><<a href="mailto:bernd.lentes@helmholtz-muenchen.de">bernd.lentes@helmholtz-muenchen.de</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Hi,<br>
<br>
Currently everything is clear.<br>
Thanks for your help</blockquote><div><br></div><div>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.</div>
<div><br></div><div>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.</div>
<div><br></div><div>-JR</div></div>