To specify load balancing settings for a disk

1. Open the DMP DSMs folder in the VEA console's tree view.
2. Select the disk that has the load balancing settings you want to change.

   Note that opening the Disks folder and clicking a disk that is under DMP DSMs control is an alternate way to select a disk.

3. Make sure the DMP DSMs tab is selected in the right pane, right-click one of the displayed paths, and then select Device Settings from the path context menu.
4. The Device Settings welcome screen appears. Click Next to continue.
5. The Select Device Settings parameters screen appears.

   Select one of the following load balancing options:

   • Round robin (Active/Active)

     This option ensures that load balancing is used for data transfers to and from a disk. With this setting, DMP DSMs configures all paths to the disk as active and enables paths, each in turn, in a round-robin fashion for data transfer.

   • Dynamic Least Queue Depth

     This option ensures that load balancing is used for data transfers to and from an array. With this setting, DMP DSMs configures all paths to the array as active and selects the path with the least number of I/O requests in its queue for a data transfer.

   • Balanced Path

     This policy is designed to optimize the use of caching in disk drives and RAID controllers. The size of the cache depends on the characteristics of the particular hardware. Generally, disks and LUNs are logically divided into a number of regions or partitions. I/O to and from a given region is sent on only one of the active paths. Adjusting the region size to be compatible with the size of the cache is beneficial so that all the contiguous blocks of I/O to that region use the same active path. The value of the partition size can be changed by adjusting the value of the tunable parameter, Block Shift.

     More details about this option are available.

   • Weighted Paths

     This option ensures that load balancing is used for data transfers to and from an array. With this setting, DMP DSMs configures all paths to the array as active and selects the path with the lowest weight for data transfer. The user assigns weights to designate which path is favored. If two or more paths have the same weight and are the lowest weight of all paths, then these paths are used each in turn, in round-robin fashion, for the data transfer.

   • Round robin with Subset

     This option ensures that load balancing is used for data transfers to and from an array. With this setting, DMP DSMs configures all paths to the array as active and uses a subset of paths each in turn, in round-robin fashion, for data transfer. The user specifies the subset of paths. The remaining paths are in standby mode.

   • Least Blocks

     This option ensures that load balancing is used for data transfers to and from an array. With this setting, DMP DSMs configures all paths to the array as active and selects the path with the least number of blocks of I/O in its queue for data transfer.

   • Fail Over Only (Active/Passive)

     This option has one primary path with the remaining path or paths on standby (backups) that are used when the current primary path fails. The primary path is the only path that is used to transfer data. This option does not provide load balancing among paths. DMP DSMs chooses a path to be the primary path. However, you may choose a specific path to be the primary path.

   Click Next to continue.

6. The Device Settings summary screen appears displaying the settings for the array. Review the settings and click Finish to apply the settings and exit the wizard.

   For some load balance policies, such as round robin with Subset, additional specifications are required. The Array Settings wizard displays a screen before the summary screen to collect these specifications. Click Next after setting these specifications to continue to the summary screen.