How collocation affects reclamation

If collocation is enabled and reclamation occurs, the server tries to move the files for each client node, group of client nodes or client file space onto a minimal number of volumes.

If the volumes are manually mounted, the mount operators must:

Be aware that a tape volume might be rewound more than once if the server completes a separate pass to move the data for each client node or client file space.
Mount and dismount multiple volumes to allow the server to select the most appropriate volume on which to move data for each client node or client file space. The server tries to select a volume in the following order:
1. A volume that already contains files belonging to the client file space or client node
2. An empty volume
3. The volume with the most available space
4. Any available volume

If collocation is disabled and reclamation occurs, the server tries to move usable data to new volumes by using the following volume selection criteria, in the order shown:

The volume that contains the most data
Any partially full volume
An empty predefined volume
An empty scratch volume

If you specify collocation and multiple concurrent processes, the server attempts to move the files for each collocation group, client node, or client file space onto as few volumes as possible. However, if files belonging to a single collocation group (or node or file space) are on different volumes to begin with and are being moved at the same time by different processes, the files might be moved to separate output volumes. For details about multiple concurrent reclamation processing, see Optimizing drive usage using multiple concurrent reclamation processes.

For more information, see Reducing the time to reclaim tape volumes with high capacity.