Load Balance Policy
Load Balance Policy is a method of equalizing the I/O traffic over each path by
systematically dividing the load among multiple paths.
• Failover Policy – No load balancing. With Automatic Load Balancing
disabled, the first path discovered is the primary path. I/Os follow the active
path until it fails, then they change to next available path. Each LUN uses
only one active path.
*See “Automatic Load Balancing for Failover Policy”
• Round Robin Policy – I/Os follow all active paths, changing paths at the
specified I/O count. You can set the I/O count in the General tab of the
Advanced Settings dialog box.
• Round Robin with Subset Policy – One or more paths are designated as
standby. I/Os follow all active paths, changing at the specified I/O count. You
can set the I/O count in the General tab of the Advanced Settings dialog box.
• Least Queue Depth Policy – I/Os follow the path with the least number of
requests queued.
Note that you can enable Automatic Load Balancing for LUNs with policy set to
Automatic Load Balancing for Failover Policy
The Promise MPIO solution can load balance the paths for your LUNs with load
balance policy set to Failover.
With Automatic Load Balancing enabled, the LUNs set to Failover policy are
automatically redistributed among all available paths when:
• A path fails
• A failed path comes back online
• A new path is added
Automatic Load Balancing, when enabled, provides optimal data throughput for
LUNs set to Failover policy.
Note that Automatic Load Balancing has NO effect upon LUNs set to Round
Robin, Round Robin with Subset, or Least Queue Depth.
Enabling Automatic Load Balancing
To enable automatic load balancing:
From the Operations menu, choose Auto Load Balance.
When you see a checkmark beside Auto Load Balance in the Operations menu,
this feature is enabled.
