Specifications

Quorum/Witness
Most Reliable Least Reliable
* While CONFIRM_SO is highly reliable (depending upon the knowledge of the administrator), it has
lower availability due to the fact that automatic failover is turned off.
Quorum/Witness
Quorum/Witness Server Support Package for LifeKeeper
Feature Summary
The Quorum/Witness Server Support Package for LifeKeeper (steeleye-lkQWK) combined with the
existing failover process of the LifeKeeper core allows system failover to occur with a greater degree
of confidence in situations where total network failure could be common. This effectively means that
local site failovers and failovers to nodes across a WAN can be done while greatly reducing the risk of
“split-brain” situations. The package will provide a majority-based quorum check to handle clusters
with greater than two nodes. This additional quorum logic will only be enabled if the witness support
package is installed.
Using one or more witness servers will allow a node, prior to bringing resources in service after a
communication failure, to get a “second opinion” on the status of the failing node. The witness server
is an additional server that acts as an intermediary to determine which servers are part of the cluster.
When determining when to fail over, the witness server allows resources to be brought in service on a
backup server only in cases where it verifies the primary server has failed and is no longer part of the
cluster. This will prevent failovers from happening due to simple communication failures between
nodes when those failures don’t affect the overall access to, and performance of, the in-service node.
During actual operation, for the initial implementation, all other nodes in the cluster will be consulted,
including the witness node(s).
Package Requirements
In addition to the requirements already discussed, this package requires that standard, licensed
LifeKeeper core be installed on the server(s) that will act as the witness server(s). Note: As long as
communication paths are configured correctly, multiple clusters can share a single quorum/witness
server (for more information, see “Additional Configuration for Shared-Witness Topologies” below).
All nodes which will participate in a quorum/witness mode cluster, including witness-only nodes,
should be installed with the Quorum/Witness Server Support Package for LifeKeeper. If using the
tcp_remote quorum mode, the hosts configured in QUORUM_HOSTS within /etc/default/LifeKeeper
are not required to be installed with the Quorum/Witness Server Support Package for LifeKeeper.
106Configuration