[DRBD-user] DRBD and KVM for a HA-Cluster ?

Lentes, Bernd bernd.lentes at helmholtz-muenchen.de
Mon Jan 10 20:46:29 CET 2011

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

JR wrote: 

>Yea I was out of pocket for a few days, but basically, you end up with 3 DRBD devices, 1 per VM/service right?  

Yes. And every DRBD device on his own LV. Same thing on the second node.

>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.

That does *not* mean, that both identical vm's are running simultaneously on the two nodes, right ?

>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.

Don't I need a cluster aware FS for that short period of time when both are running ? What mechanism for synchronization do you mean ?
Can I realise the Live migration with cluster tools, or with KVM tools ? If I use KVM tools, don't they interfere with the HA-Software ?


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