4 Nodes cluster

[daosheng]

Hi All

A cluster configured with 4 nodes with one lock disk. My question is if 2 of the nodes failed, the cluster will be reformed itself(The lived 2 nodes compete the lock disk, then TOC another node?)
example:
Node A, B, C, D
C is failed, then D is failed too. Now what will happened?
1) A and B will compete the lock disk, if A wins the lock disk, then the B will crash.
Or .
2)A and B will do nothing with the cluster runing normally?

[Duncan Edmonstone]

If C fails and the cluster is able to reform as a 3 node cluster, then D fails, the 2 remaining nodes will do nothing as they will already have quorum (2/3 = 66%)

If C and D fail at the same time, but A nd B can still communicate with each other, only one node in the remaining cluster will race for the cluster lock, which assuming C and D are really down it will win. It will then be able to reform the cluster as a 2-node cluster.

All described in the manual here:

http://docs.hp.com/en/B3936-90122/ch03s02.html#babbgfdh

HTH

Duncan

[Avinash Agarkar]

Hi,

In this sinario if any 3 nodes will down the cluster will be totaly down any 2 nodes will down then cluster will be safe.

Thanks,
Avinash

[Stephen Doud · Accepted solution]

Serviceguard response to an unexpected departure of a node is determined by quorum rules. An abrupt departure can be the result of HB network failure, or reboot/panic/power-failure.

Greater-than-50% of quorum (>50%)
---------------------------------
If the number of nodes remaining in HB contact with one another comprise more than 50% of the original membership, these nodes automatically reform a cluster. Packages that were orphaned as a result of the reformation are adopted by the next-in-line active node if package "global" (AUTO_RUN) and "node switching" are enabled for that package and node.

Equal-to-50% of quorum (=50%)
-----------------------------
If a HB protocol failure occurs between half of the cluster membership and the other half, cluster arbitration is required to prevent split-brain clusters. The nodes seek out the arbitration device to gain authorization to form a new cluster. The first half to contact the arbitration device and receive authorization reforms a reduced cluster.

If the other half of the cluster membership is still active, but late in addressing the arbitration device, it is forced to TOC (reboot) to preserve data integrity (it's packages could possibly be adopted by the reforming sub-cluster).

Less-than-50% of quorum (<50%)
------------------------------
A node or nodes that find themselves in a minority of the original cluster membership are forced to TOC to preserve data integrity (see previous paragraph).

[daosheng]

Problem is solved