Veritas Volume Manager 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

Chapter 3, Administering Dynamic Multipathing (DMP)
Administering DMP Using vxdmpadm
121
Displaying the I/O Policy
To display the current and default settings of the I/O policy for an enclosure, array or
array type, use the vxdmpadm getattr command.
The following example displays the default and current setting of iopolicy for JBOD
disks:
# vxdmpadm getattr enclosure Disk iopolicy
ENCLR_NAME DEFAULT CURRENT
---------------------------------------
Disk balanced MinimumQ
The next example displays the setting of partitionsize for the enclosure enc0, on
which the balanced I/O policy with a partition size of 2MB has been set:
# vxdmpadm getattr enclosure enc0 partitionsize
ENCLR_NAME DEFAULT CURRENT
---------------------------------------
enc0 1024 2048
Specifying the I/O Policy
You can use the vxdmpadm setattr command to change the I/O policy for distributing
I/O load across multiple paths to a disk array or enclosure. You can set policies for an
enclosure (for example, HDS01), for all enclosures of a particular type (such as HDS), or for
all enclosures of a particular array type (A/A for Active/Active, or A/P for
Active/Passive).
Note Starting with release 4.1 of VxVM, I/O policies are recorded in the file
/etc/vx/dmppolicy.info, and are persistent across reboots of the system.
Do not edit this file yourself.
The following policies may be set:
◆ adaptive
This policy attempts to maximize overall I/O throughput from/to the disks by
dynamically scheduling I/O on the paths. It is suggested for use where I/O loads can
vary over time. For example, I/O from/to a database may exhibit both long transfers
(table scans) and short transfers (random look ups). The policy is also useful for a
SAN environment where different paths may have different number of hops. No
further configuration is possible as this policy is automatically managed by DMP.