HP-UX 11i v3 Native Multi-Pathing for Mass Storage (August 2012)

For an example on how the health property changes when a target port becomes unavailable, see

Native Multi-Pathing: A Concrete Example.

LUN and lunpath attributes

The scsimgr command reads and sets the multi-pathing related attributes of LUN components. All

the LUN and lunpath attributes are described in details in the

scsimgr SCSI Management and

Diagnostics Utility white paper. The following table summarizes LUN and lunpath attributes of interest

for multi-pathing:

Component Attributes

LUN Generic:

hw_path, wwid, serial_number, vid, pid, total_path_cnt,

transient_secs, leg_mpath_enable, lpt_lockdown, uniq_name

Disk LUNs:

path_fail_secs, load_bal_policy, infinite_retries_enable,

preferred_path, pref_tport, alua_enabled

lunpath Generic:

lunid, hw_path

Setting I/O load balancing for disk devices

The following examples show how the system administrator can set the I/O load balancing policy

and other related attributes. The attribute values can be modified temporary with the scsimgr

set_attr command or persistently across system reboots with the scsimgr save_attr

command. The latter command can also be used to persistently restore attribute default values. For

more information, see scsimgr(1M).

Disk LUN load balancing selection

The default load balancing policy for disk devices is round_robin:

# scsimgr get_attr -D /dev/rdisk/disk17 -a load_bal_policy

SCSI ATTRIBUTES FOR LUN : /dev/rdisk/disk17

name = load_bal_policy

current = round_robin

default = round_robin

You can change the policy to cell locality based round robin as follows:

# scsimgr set_attr -D /dev/rdisk/disk17 -a load_bal_policy=cl_round_robin

# scsimgr get_attr -D /dev/rdisk/disk17 -a load_bal_policy

SCSI ATTRIBUTES FOR LUN : /dev/rdisk/disk17

name = load_bal_policy

current = cl_round_robin

default = round_robin

saved =

To change the load_bal_policy attribute to preferred_path, you must set the

preferred_path attribute to the hardware path of the preferred lunpath. The following commands

show how to find the lunpaths hardware paths mapping to /dev/rdisk/disk17 and how to select

one of them as the preferred path. For optimal performance, the preferred lunpath must correspond to

an optimized controller or target port group. In the following example, the assumption is the target

port 0x500508b3009097f9 is optimized for I/O transfer to disk17, and we want to make the

change persistent across system reboots: