HP MPIO Full Featured DSM for P6x00 family of Disk Arrays 4.04.00 Installation and Reference Guide (757324-001, May 2014)

NOTE:
• All devices that are part of the logical unit group, have the same subset setting.
• The subset setting is not applicable for devices that have the No Load Balancing policy
enabled.
• The subset setting for a given LUN is persistent across Load Balance policies and host system
reboots.
• The paths that are part of the subset are reported as "Active" and other paths are reported
as "Available".
You can modify (enable or disable and add or remove paths) the subset setting for a given
LUN through the HP DSM CLI. The current version of HPDSM Manager does not support subset
setting operations. For more information, see “Chapter 4”.
Use case scenarios
Following are some scenarios where subset based load balance settings are used:
NOTE: In a host system, for the multipath solution to function properly, all the devices must be
accessible through all the available paths.
1. Using subset setting to group paths for devices based on its usage— When a particular device
has to use only a set of paths for I/O, enable subset for that device to include only the required
paths. This could be used in the following cases:
• When high performing paths are required by devices running critical applications. The
other available paths can be used by non-critical applications.
• When some paths needs to be exclusively used by a particular device, excluding these
paths from the subset members of other devices.
2. Using subset setting during maintenance in a fabric— When a set of components in a fabric
(like switches, and HBAs) are under maintenance and the paths leading through these
components are not to be used for I/O, you can enable subset to exclude the paths for that
device until maintenance is complete.
Adaptive Load Balance
The HP MPIO EVA DSM implements array specific load balancing algorithms that utilize certain
features supported by the disk arrays, to deliver better performance for host I/O requests. The
Adaptive Load Balance (ALB) setting is supported on a per logical unit basis and works in
conjunction with the load balancing policies supported by the DSM.
By default, ALB is disabled for the newly discovered LUN. If the newly discovered LUN is part of
any logical unit group, the ALB setting of the existing group prevails.
NOTE:
• All devices that are part of the Logical Unit Group, has the same ALB setting.
• The ALB setting is not applicable for devices that have the No Load Balancing policy
enabled.
• The ALB setting for a given LUN is persistent across host system reboots.
You can modify (enable or disable) the ALB setting for a given LUN either through the HP
MPIO DSM Manager or HP DSM CLI. For more information, see “Chapter 4”.
14 Load balancing