cluster lock

[Shah Gaurang B.]

Dear Friends,

I am not able to understand the purpose of cluster lock . I read documents but not able to understand the purpose of it and i have confusion tha will the disks used in package be in mirrored position on both node if i have two node cluster or single single disk of both node access by both node in condition of exclusive mode ?

Pl freinds guide me . how it works ?

[Steven E. Protter · Accepted solution]

Shalom Shah,

The purpose of a cluster lock is to resolve contention between two nodes of a cluster. In the event that communications are lost both nodes try and grab the cluster lock disk.

The node that succeeds survies, the node that fails does a TOC, transfer of control and boots.

It prevents data corruption where both nodes try and be the primary at the same time, otherwise known as split brain syndrome.

You can use a quorum server to replace cluster lock disk, but that requires another system.

SEP

[Prashanth.D.S]

Hi,

The cluster lock is used as a tie-breaker only for situations in which a running cluster fails and, as MC/ServiceGuard attempts to form a new cluster, the cluster is split into two subclusters of equal size.

Each sub-cluster will attempt to acquire the cluster lock. The sub-cluster
which gets the cluster lock will form the new cluster, preventing the possibility of two sub-clusters running at the same time. If the two sub-clusters are of unequal size, the sub-cluster with greater than 50% of the nodes will form the new cluster, and the cluster lock is not used.

Every hour ServiceGuard checks the availability of configured cluster lock disks. A failed check is logged to syslog.log

Quorum Server can be used in case of the nodes are more than 4 nodes.

Best Regards,
Prashanth

[Serviceguard for Linux]

Hopefully this whaite paper will explain it more clearly.

http://docs.hp.com/en/B3936-90078/B3936-90078.pdf