9.5 HP P4000 DSM for MPIO Deployment Guide (AX696-96111, September 2011)

Figure 3 Multi-site SAN VIPs with MPIO
Setting the Microsoft DSM MPIO load balancing policy
When you connect application servers to volumes, you can also set the MPIO load balancing policy
in the iSCSI Initiator.
Supported load balancing options
Only two load balancing options are supported, Fail Over and Round Robin. For the Microsoft DSM
with Windows 2003 Server, only the Fail Over Only option is supported.
• Fail Over Only – Also called active/passive MPIO. Two (or more) I/O paths are built between
the server and the storage. One path is actively used for I/O to the storage. The other paths are
available for failover only in the event the primary path goes down.
• Round Robin – Also called active/active MPIO. Two (or more) I/O paths are built between the
server and the storage. All paths are actively used for I/O to the storage.
In the HP DSM for MPIO, Vendor Specific is selected by default. This option is the same as selecting
Fail Over Only and will not be available after you select another option. In the Microsoft DSM, Fail
Over Only is the default selection for all Windows versions, except for Windows 2008 R2, for which
Round Robin is the default.
The MPIO load balancing policy affects the number of iSCSI connections created to the volume. The
number of connections also differs based on whether you are using the HP DSM for MPIO or the
Microsoft DSM. “HP DSM for MPIO with two NICs in the server and Failover MPIO load balancing”
(page 8) through “Microsoft DSM with two NICs in the server and Round Robin MPIO load balancing”
(page 9) show the connections created with applications servers that have two NICs.
Figure 4 HP DSM for MPIO with two NICs in the server and Failover MPIO load balancing
8 Connecting volumes with MPIO