Sun Cluster 3.1 Concepts Guide

Cluster Time

Time between all nodes in a cluster must be synchronized. Whether you synchronize the cluster nodes with any outside time source is not important to cluster operation. The SunPlex system employs the Network Time Protocol (NTP) to synchronize the clocks between nodes.

In general, a change in the system clock of a fraction of a second causes no problems. However, if you run date(1), rdate(1M), or xntpdate(1M) (interactively, or within cron scripts) on an active cluster, you can force a time change much larger than a fraction of a second to synchronize the system clock to the time source. This forced change might cause problems with file modification timestamps or confuse the NTP service.

When you install the Solaris operating environment on each cluster node, you have an opportunity to change the default time and date setting for the node. In general, you can accept the factory default.

When you install Sun Cluster software using scinstall(1M), one step in the process is to configure NTP for the cluster. Sun Cluster software supplies a template file, ntp.cluster (see /etc/inet/ntp.cluster on an installed cluster node), that establishes a peer relationship between all cluster nodes, with one node being the “preferred” node. Nodes are identified by their private host names and time synchronization occurs across the cluster interconnect. The instructions for how to configure the cluster for NTP are included in the Sun Cluster 3.1 Software Installation Guide.

Alternately, you can set up one or more NTP servers outside the cluster and change the ntp.conf file to reflect that configuration.

In normal operation, you should never need to adjust the time on the cluster. However, if the time was set incorrectly when you installed the Solaris operating environment and you want to change it, the procedure for doing so is included in the Sun Cluster 3.1 System Administration Guide.