[DRBD-user] Off-site Quorum Provider?

Digimer linux at alteeve.com
Fri Mar 2 23:21:26 CET 2012

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

On 03/02/2012 04:41 PM, Robinson, Eric wrote:
> We have two geographically separate data centers connected by 4 x
> Gigabit links (in 2 trunks). Our HA clusters are distributed between the
> data centers, with each node of a 2-node cluster in a separate data
> center. (In the case of our 3-node clusters, 2 nodes are in one data
> center and the 3rd node is in the other data center.) Cluster membership
> information is communicated though both of the Gigabit trunks, where
> each trunk is a separate Corosync ring. DRBD is replicated through one
> of the trunks.
> Question: If the links between the data centers are severed, split brain
> will occur. What is the best way to provide quorum from a third location
> out on the Internet?
> Note: I posted this question to the Linux HA list, too, because I was
> not sure which was better suited.
> --
> Eric Robinson

Couple of comments;

As-is, quorum can't be gained without simple majority. Thus, in a
partition, your location with just one node can not become quorate.

Corosync doesn't use, to my understanding, both rings at the same time.
It's a simple fail-over configuration where the backup ring comes into
use only in the event of a failure in the main ring.

Quorum over a stretch cluster is always tricky. With sufficient speed,
you could look at qdisk, but that would likely induce as many problems
as it solved.

E-Mail:              digimer at alteeve.com
Papers and Projects: https://alteeve.com

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