These parameters can be used to specify how the system must perform write operations on disk libraries that have multiple mount paths. Two parameters for mount path usage can be configured. They are:
Fill and Spill Mount Paths (Use new mount paths only as needed)
If this option is selected the system completely fills the disk space (based on the space allocation established for the individual mount paths) before writing to another mount path. Use this option when you want the data to be consolidated, without any fragmentation.
The system will use the mount path in the order in which the mount path was added to the library. For example, a disk library has 3 mount paths (A, B, C) configured. All the jobs will be directed to mount path A as it was created first. Mount paths B and C will be used for additional writers in the order in which they were added to the disk library. Note that as long as a active volume exists in any of the mount paths, the consecutive backups will continue to use that mount path.
Spill and Fill Mount Paths (load balance use of mount paths)
If this option is selected the system writes to all the mount paths in parallel if you have established sufficient number of writers. Use this option to obtain maximum throughput, especially when you have several mount paths. However the data will be fragmented between the available mount paths.
Note that when this option is selected, the system will use the Least Recently Used (LRU) mount path. (As opposed to the mount path with least used capacity.)
For example, a disk library with 3 mount paths (A, B, C) and if two 3-stream storage policies (SP_1_1, 2 and 3 and SP_2_1, 2 and 3) are used for running simultaneous backups, the jobs are run as follows: (Assuming that the backups are run for the first time.)
SP_1_1 > Mount Path A
SP_2_1 > Mount Path B
SP_1_2 > Mount Path C
SP_2_2 > Mount Path A
SP_1_3 > Mount Path B
SP_2_3 > Mount Path C
Note that this order may change subsequently, depending on the LRU condition of the mount path.
To illustrate the usage of the above mentioned options, consider the following example:
Assume that a disk library that allows multiple writes is configured with two mount paths. Start two jobs - the jobs may either be run concurrently, or individually, one after another. If the Fill and Spill mount paths option is selected, both jobs will use the first mount path. If the Spill and Fill mount paths option is selected, the first job will use the first mount path and the second will use the second mount path.
Note that data protection operations will continue with an available mount path if a required mount path is not available, thereby taking precedence over the option specified for mount path usage. For example, assume that that there are two mount paths, with the Spill and Fill mount path option selected. If one of the mount paths is not available, all data protection operations will use the available mount path.
Procedure
-
From the CommCell Browser, expand to Storage Resources | Libraries.
-
Right-click the appropriate library, and then click Properties.
-
Click the Mount Paths tab.
-
Select either Fill and spill mount paths or Spill and fill mount paths.
-
Click OK.