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ExpressCluster X 2.0 for Windows Reference Guide - Nec

ExpressCluster X 2.0 for Windows Reference Guide - Nec

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Understanding failover policy<br />

Section II Resource details<br />

What is a group?<br />

A failover policy is a rule that determines a server to be the failover destination from multiple<br />

servers, and it is defined by the properties of a group. When you configure the failover policy,<br />

avoid making certain servers more heavily loaded at a failover.<br />

The following describes how servers behave differently depending on failover policies when a<br />

failover occurs using example of the server list that can fail over and failover priority in the list.<br />

<br />

Server status Description<br />

o Normal (properly working as a cluster)<br />

od Suspended (not recovered as a cluster yet)<br />

× Stopped (cluster is stopped)<br />

3-node configuration:<br />

Group<br />

Order of server priorities<br />

1 st priority server 2 nd priority server 3 rd priority server<br />

A server1 server3 server2<br />

B server2 server3 server1<br />

2-node configuration:<br />

Group<br />

Order of server priorities<br />

1 st priority server 2 nd priority server<br />

A server1 server2<br />

B server2 server1<br />

It is assumed that the group startup attributes are set to auto startup and the failback attributes<br />

are set to manual failback <strong>for</strong> both Group A and B. It is also assumed that the servers are<br />

configured not to recover automatically from the status of being suspended. Whether to<br />

per<strong>for</strong>m auto recovery from the suspended status is set ON/OFF of Auto Return on the Auto<br />

Recovery tab in Cluster Properties.<br />

• If groups of different failover exclusive attributes co-exist in a cluster, they do not interfere<br />

with each other. For example, a group of full exclusive attributes may start on a server<br />

where a group of non-exclusive attributes is active, and vice versa.<br />

• For groups whose failover exclusive attributes are normal or full, the server which they start<br />

up or fail over is determined by the failover priority to the server. If a group has two or more<br />

servers of the same failover priority, it is determined by the order of numbers, the specific<br />

symbols and alphabets of the group name.<br />

• The failover priority of the WebManager group is determined by the server priority. You<br />

can specify server priority on the Master Server tab in Cluster Properties.<br />

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