Product manual

Features and Settings
461
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” on page 460.
• 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.
If LUN Affinity is enabled do NOT use Round Robin. See “Making Controller
Settings” on page 86 or page 216.
• 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.
If LUN Affinity is enabled, you can use Round Robin with Subset. See
“Making Controller Settings” on page 86 or page 216.
• 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
Failover. See “Automatic Load Balancing for Failover Policy” on page 460.
Changing Load Balance Policy Settings
To change load balance policy settings:
1. Do one of the following actions:
• From the Operations menu, choose Change Load Balance Policy.
• In Tree View, highlight a LUN and click the Change Load Balance
Policy icon.
• In Tree View, right-click a a LUN and choose Change Load Balance
Policy from the popup menu.
The Change Load Policy dialog box appears with the Load Balance Policy
tab displayed.
2. Click the option button for one of the Load Policies.
• Failover Policy
• Round Robin Policy
• Round Robin with Subset Policy
• Least Queue Depth Policy