Two primary functions are required to implement a high availability cluster:
- A way to handle load balancing and individual host fail-over.
- A way to synchronize storage so that all servers provide the same view of the data they serve.
Debian includes meta packages that bring together software from the Linux High Availability project, including cluster-agents and resource-agents, two of the higher-level meta packages. These packages install various agents that are useful in coordinating and managing load balancing and fail-over. In some cases, a master server is designated to distribute the processing load among other servers.
Data synchronization is handled by using shared storage and any of the filesystems that provide for multiple accesses and shared files, such as NFS or AFS.
High Availability clusters generally use standard software, along with software that is readily available to manage the dynamics of such environments.
