VCS Failover
Veritas Cluster Server (VCS) is a High-availability cluster software, for Unix, Linux and Microsoft Windows computer systems, created by Veritas Software (now part of Symantec).
Veritas Cluster enables one system to failover to the other system. Both system configurations are predefined.
Example VCS cluster will have an alias ‘A’ which will point to a one backend machine (at any given point).. when that machine fail then alias ‘A’ will point to new backend (list of backend machines are predefined).
All processes already running will get killed when machine fails (they will have to be brought up in next failover machine).. they can be automatically be brought up (if configured in start scripts)
VCS uses two components, LLT and GAB to share data over the private networks among systems.
These components provide the performance and reliability required by VCS.
log files are located under /var/VRTSvcs/log and list of failover candidates can be seen in /etc/lltab.
Few things are to be understood..
When machines fails you will new backend won’t have local data (/tmp,/var/tmp). Most of the times it’s used with SAN storage (like Databases or other critical applications).
