scsimgr SCSI Management and Diagnostics utility on HP-UX 11i v3 (March 2008)

These tunables need to be fine tuned to meet the following requirements for an optimal operation:

• All HP disk devices with the product identifier (pid) ST3360LCB, require path_fail_secs to be

set at least to 160 seconds. In addition these disk arrays exhibit some degradation in

performance if I/O requests are distributed in a round robin manner. Optimal performances

are obtained with the least_cmd_load policy, which distributes I/O to the I/O path with the

least load.

• All HP disk devices with pid ST39103FC2, can handle only up to 4 concurrent I/O requests.

• disk0 is a JBOD connected to the system through a very slow and unreliable link. It requires

path_fail_secs to be set at least to 240 seconds.

Note: This example of different operational requirements is theoretical. It is just intended to illustrate

the capabilities of the stack.

The values of these attributes at the esdisk driver global level, determine the default behavior for all

disk devices bound to the esdisk driver.

# scsimgr get_attr -N /escsi/esdisk -a path_fail_secs -a load_bal_policy -a max_q_depth

SCSI ATTRIBUTES FOR DDR ENTRY : /escsi/esdisk

name = path_fail_secs

current = 120

default = 120

saved =

name = load_bal_policy

current = round_robin

default = round_robin

saved =

name = max_q_depth

current = 8

default = 8

saved =

You can perform the following to meet the above requirements:

1 Add 2 settable attribute scopes covering respectively HP disk devices with pid:

ST3360LCB and ST39103FC2.

# scsimgr -f ddr_add -N "/escsi/esdisk/0x0/HP /ST3360LCB "

scsimgr: settable attribute scope '/escsi/esdisk/0x0/HP /ST3360LCB '

added successfully

# scsimgr ddr_add -N "/escsi/esdisk/0x0/HP /ST39103FC2 "

scsimgr: settable attribute scope '/escsi/esdisk/0x0/HP /ST39103FC2 '

added successfully

Note: To ease the determination of settable attribute scope names and limit user errors, starting with the March

2008 release of HP-UX 11i v3, the command option ‘ddr_name’ has been introduced to automatically generate

a settable attribute scope name from a LUN. The user can cut and paste the name to register it with the

command ‘scsimgr ddr_add’. For example to generate a settable attribute scope name covering all devices with

the same peripheral type and vendor identifier as disk100 you can run the following command:

# scsimgr ddr_name -D /dev/rdisk/disk15 vid

SETTABLE ATTRIBUTE SCOPE

"/escsi/esdisk/0x0/COMPAQ "

2 Set path_fail_secs to 160 seconds, load_bal_policy to least_cmd_load for HP disk devices

with pid: ST3360LCB.