Allocation and use of scratch and predefined FILE storage pool volumes

Answer

When multiple directories are specified for a FILE device class, associated storage pools that use the scratch volumes (automatic allocation) will see volume allocation and usage in a round-robin fashion. Predefining volumes with the DEFINE VOLUME COMMAND will allocate volumes in a round-robin fashion but usage will be in alphabetical order due to internal volume sorting. When predefining volumes, the Tivoli Storage Manager server will use all of the volumes in one directory before using the volumes in another directory.

The alphabetical sorting does not impact auto-allocation of FILE device class volumes because only a single empty volume exists on each alphabetical sort. Because of this, auto-allocation of FILE device class volumes will result in an apparently congruent usage methodology.

Example:

Suppose two drives exist (C: and D:) and are specified as directories for a particular FILE device class. When a storage pool uses this device class without manually defined volumes and a maxscratch parameter greater than 0, usage and allocation will work as follows during any operation that requires space in the storage pool (such as a client backup):

1) Allocate c:\00000000.BFS

2) Sort list of empty volumes alphabetically - only choice is c:\00000000.BFS. Fill with data until full, then

3) Allocate d:\00000001.BFS

4) Sort list of empty volumes alphabetically - only choice is d:\00000001.BFS. Fill with data until full, then

5) Allocate c:\00000002.BFS

6) Sort list of empty volumes alphabetically - only choice is c:\00000002.BFS. Fill with data until full, then

7) Allocate d:\00000003.BFS

8) Sort list of empty volumes alphabetically - only choice is d:\00000003.BFS. Fill with data until full, then

9) Allocate c:\00000004.BFS

10) Sort list of empty volumes alphabetically - only choice is c:\00000004.BFS. Fill with data until full, then

11) Allocate d:\00000005.BFS

12) Sort list of empty volumes alphabetically - only choice is d:\00000005.BFS. Begin filling with data.

When six volumes are predefined to this storage pool and a procedure that consumes space on the storage pool is performed, the following occurs:

1) Allocate c:\00000000.BFS

2) Allocate d:\00000001.BFS

3) Allocate c:\00000002.BFS

4) Allocate d:\00000003.BFS

5) Allocate c:\00000004.BFS

6) Allocate d:\00000005.BFS

7) Sort list of empty volumes alphabetically: List appears as

c:\00000000.BFS

c:\00000002.BFS

c:\00000004.BFS

d:\00000001.BFS

d:\00000003.BFS

d:\00000005.BFS

This behavior is working as designed.