Server Roles

Each server that participates in data synchronization can be set up to fill any one of the roles in a cluster. The administrator designs the NAS cluster layout and assigns roles to each of the NAS that are part of the NAS cluster. The same information on the role of each NAS must be given to all NAS in order for the cluster to work properly.

All participating servers have the potential to become the Sync Primary.

Role Description Participates in DSync

Sync Primary

Used for all reads and writes to the distributed data storage. All other cluster members communicate with this server when requesting state and session data.

Y

Sync Backup

Updated each time a write is made to the primary.

Any number of Sync Servers, up to a maximum set by the administrator (the default number is one), that mirror the information on the Sync Primary. The job of the Sync Backup is to be available to become Sync Primary if the Current Sync Primary fails.

Y

Sync Alternate

Does not contain any data but is ready to be promoted to Sync Backup if a server fails.

A server listed in the Sync Servers registry key that is eligible to become a Sync Backup. When the number of Sync Backups falls below the set maximum, the Sync Alternate with the highest priority relative to other Sync Alternates is promoted to Sync Backup.

Each Sync Alternate performs work similar to the work of a Sync Local until the Sync Alternate is promoted to a Sync Backup.

Y

Sync Local

Sync Local servers use data in the distributed store and send data to be stored in the distributed store. Sync Locals are not eligible to become Sync Servers.

Each Sync Local contacts each of the servers listed in its SyncServers registry key until it finds a Sync Primary. When it finds the primary, it becomes active in the NAS cluster. If the Sync Local goes through its SyncServers registry keys without finding a Sync Primary, the Sync Local assumes the cluster is down and acts as a local server.

N