Veritas Cluster Server

Veritas Cluster Server is a high-availability cluster software for unix, linux and Microsoft windows computer systems. It is an availability clustering solution that manages the availability of application services, such as Db2 database, by enabling application failover. The state of each individual cluster node and its associated software services are regularly monitored.

Failover

Failover is a process. Whenever a primary system, network or a database fails or is abnormally terminated, then a Failover acts as a standby which helps resume these operations.

Failover Cluster

Failover cluster is a set of servers that work together to provide High Availability (HA) or Continuous availability (CA). As mentioned earlier, if one of the servers goes down another node in the cluster can take over its workload with minimal or no downtime. Some failover clusters use physical servers whereas others involve virtual machines (VMs).

CA clusters allow users to access and work on the services and applications without any incidence of timeouts (100% availability), in case of a server failure. HA clusters, on the other hand, may cause a short hiatus in the service, but system recovers automatically with minimum downtime and no data loss.

A cluster is a set of two or more nodes (servers) that transmit data for processing through cables or a dedicated secure network. Even load balancing, storage or concurrent/parallel processing is possible through other clustering technologies.

Veritas Cluster Server (VCS)

Veritas Cluster Server is a high-availability cluster software for Unix, Linux and Microsoft Windows computer systems.

Veritas Cluster Server connects multiple, independent systems into a management framework for increased availability. Each system or node runs its own operating system and cooperates at the software level to form a cluster. VCS links commodity hardware with intelligent software to provide application failover and control. So when a node or a monitored application fails, other nodes take over and bring up services elsewhere in the cluster.

How VCS detects failure

VCS detects failure by issuing specific commands or scripts to monitor the overall health of an application. VCS also determines the health of underlying resources supporting the application, such as network interfaces or file systems.

VCS uses a redundant network heartbeat to differentiate between the loss of a system and the loss of communication between systems.

How VCS ensures application availability

When VCS detects an node or application failure, VCS brings application services up on a different node in a cluster. VCS virtualizes IP addresses and system names, so client systems continue to access the application without any interruption.

Comapanies which installed Veritas Software : DHL , Orange , Symantec , IBM , Akamai , BT