Guidelines for Managing a Failover
If the primary cluster
fails, the application must be switched over to the secondary cluster as soon
as possible. To enable the secondary cluster to take over, the DNS must be
The DNS associates a client with the logical
hostname of an application. After a failover, the DNS mapping to the primary
cluster must be removed, and a DNS mapping to the secondary cluster must be
created. Figure A–6 shows
how the DNS maps a client to a cluster.
Figure A–6 DNS Mapping of a Client to a Cluster
To update the DNS, use the nsupdate command. For
information, see the nsupdate(1M) man
page. For an example of how to manage a failover, see Example of How to Manage a Failover.
After repair, the primary cluster
can be brought back online. To switch back to the original primary cluster,
perform the following tasks:
Synchronize the primary cluster with the secondary cluster
to ensure that the primary volume is up-to-date.
Update the DNS so that clients can access the application
on the primary cluster.