Appendix E. The CSM plug-in

The Cluster Segment Manager (CSM) is the EVMS plug-in that identifies and manages cluster storage. The CSM protects disk storage objects by writing metadata at the start and end of the disk, which prevents other plug-ins from attempting to use the disk. Other plug-ins can look at the disk, but they cannot see their own metadata signatures and cannot consume the disk. The protection that CSM provides allows the CSM to discover cluster storage and present it in an appropriate fashion to the system.

All cluster storage disk objects must be placed in containers that have the following attributes:

• cluster ID that identifies the cluster management software

• node ID that identifies the owner of the disk objects

• storage type: private, shared, or deported

The CSM plug-in reads metadata and constructs containers that consume the disk object. Each disk provides a usable area, mapped as an EVMS data segment, but only if the disk is accessible to the node viewing the storage.

The CSM plug-in performs these operations:

• examines disk objects

• creates containers

• uses the containers to consume disk objects

• produces data segment objects if the disk is accessible to the node