Sun Cluster Concepts Guide for Solaris OS

Cluster Time

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

In general, a change in the system clock of a fraction of a second causes no problems. However, if you run date, rdate, or xntpdate (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 System on each cluster host, you have an opportunity to change the default time and date setting for the host. In general, you can accept the factory default.

When you install Sun Cluster software by using the scinstall command, 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 host), that establishes a peer relationship between all cluster hosts. One host is designated the “preferred” host. Hosts are identified by their private host names and time synchronization occurs across the cluster interconnect. For instructions about how to configure the cluster for NTP, see Chapter 2, Installing Software on Global-Cluster Nodes, in Sun Cluster Software Installation Guide for Solaris OS.

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 System and you want to change it, the procedure for doing so is included in Chapter 9, Administering the Cluster, in Sun Cluster System Administration Guide for Solaris OS.