Red Hat CLUSTER SUITE FOR ENTERPRISE LINUX 5.1 Uživatelský manuál stáhnout pdf (Strana 11)

Introduction to Linux Clustering

quorum to unbalance the quorum voting.

Effectively, quorum allows you to make an even cluster, uneven when it comes to failovers,

so that split brain will not occur.

But what happens when you only have a two-node cluster? A failure of either node would

cause the cluster to lose quorum, as both machines have equal votes. In this case, you need a

tie-breaker vote to determine the master.

There are two ways this can be done:

1. If using a SAN/NAS, the central storage device can be used to provide the tie-breaker

vote by using a custom filesystem called a quorum disk.

2. Setup a heuristics test. This can be any program (typically something like ping) that

can provide another vote if the program completes successfully. In a two-node

cluster, the most likely candidate would be to ping the network gateway, or a remote

host1

host2

host3

host4

host5

host6

switch1

switch2

Votes = 4

host1-4 form an active cluster

Votes = 2

hosts5-6 get fenced by the others

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Red Hat CLUSTER SUITE FOR ENTERPRISE LINUX 5.1 Uživatelský manuál Strana 11