SFHA Solutions 6.0.1: Understanding single-node VCS clusters and the single-node mode
You can install Veritas Cluster Server (VCS) on a single system to configure a single-node VCS cluster. You can use VCS single-node clusters for basic application administration tasks as well as application high availability-related tasks.
For application administration, you can use Veritas Operations Manager (VOM) as a single console to manage a wide range of applications running across a variety of operating systems in your datacenter. You can perform administrative actions such as gracefully starting and stopping applications. Additionally, these tasks do not require you to undergo any application-specific or operating system-specific training.
For application high availability, you can configure application restart and system reboot as fault management remedies in single-node VCS clusters. Symantec ApplicationHA leverages VCS clustering capabilities in virtualization environments. With Symantec ApplicationHA, you can configure application restart, system reboot, and virtual system failovers, as fault management remedies.
The single-node mode is a different concept from the single-node cluster. The term single-node mode or one-node mode refers to the “-onenode” option that you can specify in the ‘hastart’ VCS commands, to start VCS on a node, without any communication links to other VCS nodes.
You can invoke a VCS node in single-node mode, irrespective of whether the node is part of a single-node cluster or a multi-node cluster. In the single-node mode, the VCS policy engine, also known as High Availability Daemon (HAD), does not communicate with the Global Atomic Broadcast (GAB) module. The node therefore cannot participate in application failover.
You cannot form a multi-node cluster by adding a single-node cluster, that is in single-node mode, to another node. To create a multi-node cluster using single-node clusters, you must first ensure that you unconfigure the single-node mode, and configure the LLT/GAB modules.
Common use cases of single-node clusters include:
- Enabling datacenter administrators to start and stop a large variety of configured applications from VOM management console without the need for specialized training in the applications or the operating systems on which the applications are loaded.
- Hosting the Coordination Point or CP Server of the VCS fencing (VxFEN) module on a single-node cluster
- Hosting an application on a single-node cluster at the disaster recovery site (remote site), to economize on hardware in a Global Cluster Option (GCO) setup. In this case you cannot configure local application failover, but you can fail over the application back to the protected site.
- Creating a single-node cluster as a first step to creating a multi-node cluster. Ensure that you do not configure VCS in single-node mode for such a cluster.
For more information on installing a single-node VCS cluster and adding it to other clusters, see:
- Creating a single-node cluster using the installer program
- Creating a single-node cluster manually
- Adding a node to a single-node cluster
- Setting up a node to join the single-node cluster
- Adding nodes using the VCS installer
- Manually adding a node to a cluster
For more information on configuring VCS in single-node mode, see:
VCS documentation for other releases and platforms, as well as Symantec ApplicationHA can be found on the SORT website