IBM Midrange System DS4000 Series Hardware Manual page 152

When you create a logical drive, you assign one of the two active controllers to own the logical
drive (called
controller ownership" on page 114) and to control the I/O between the logical drive and the
application host along the I/O path. The preferred controller normally receives the I/O
requests from the logical drive. If a problem along the data path (such as a component failure)
causes an I/O to fail, the multipath driver issues the I/O to the alternate controller.
A multipath device driver is not required when the host operating system has its own
mechanism to handle multiple I/O paths, but if not, you have to install the supplied multipath
device driver, even if your server does not has multiple paths.
Table 4-5 shows the DS5000 storage subsystem interoperability matrix of multipathing
drivers.
Table 4-5 DS5000 storage subsystem interoperability matrix of multipathing drivers
DS5000 RDAC
Win MPIO
AIX MPIO
AIX SDDPCM
LVM (HP-UX)
SDD for HP-UX
a. Included in the operating system
Load Balancing Policy
When you have multiple paths to the DS5000 storage subsystem, the driver can select
between different options about how to manage the traffic between the host and storage. The
options available for the different operative systems are shown in Table 4-6.
Table 4-6 Load Balancing Policies per OS
Operating system
AIX
Red Hat Enterprise Linux 4 Update 7
Solaris
SUSE Linux Enterprise 9 Service Pack 4
Windows
134
IBM Midrange System Storage Hardware Guide
preferred controller ownership,
Windows RHEL
2003/2008
X
X
as described in 4.1.2, "Logical drives and
SLES AIX 5L AIX
V5.3 V6.1
X
a a
X X
X X
Multipath driver Load Balancing Policy
MPIO Round robin
Selectable path priority
MPP Round robin
Least queue depth
MPxIO Round robin
MPP Round robin
Least queue depth
MPIO Round robin
Least queue depth
Least path weight
HP-UX HP-UX
11.23 11.31
X X
X