HP MPIO Full Featured DSM for SAN Virtualization Services Platform 4.01.00 installation and reference guide (5697-0237, January 2010)

3 Load balancing
Load Balancing is used to distribute I/O request across multiple paths to a logic unit for optimal usage
of paths and improve I/O performance. Depending on the load balancing policy set for a logic unit,
an appropriate path is selected based on the statistics over that path. The DSM currently supports the
following five load balance policies.
Table 3 Load balancing policies
This policy assigns equal priority to all the paths available for a device and
routes I/O request to each path in order.
Round Robin (RR)
This policy selects the path based on the service time for the outstanding I/O
requests and chooses the path with the least outstanding I/O service time for
the incoming I/O request. This is the default policy set by the DSM.
Shortest Queue Service Time
(SQST)
This policy selects the path with least outstanding I/O requests.Shortest Queue Requests (SQR)
This policy selects the path with least outstanding I/O bytes.Shortest Queue Bytes (SQB)
This policy does not implement any I/O load balancing. However, the DSM
selects a path to service all the I/O requests if preferred path is not set.
No Load Balance (NLB)
NOTE:
• The load balancing policy for a given LUN is persistent across host system reboots.
You can modify the load balancing policy for a given LUN either through the HP MPIO DSM
Manager or HP DSM CLI. See Chapter 4 for more information.
HP MPIO Full Featured DSM for SAN Virtualization Services Platform 4.01.00 installation and reference
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