the way to Change the Load Balancing Policy of a Disk

Question

[size=1.4em]Issue

This document describes how to change the load balancing policy of a disk.
Environment:

• Operating system: HP-UX version 11.31 (11i v3)
• Itanium HP Integrity servers

[size=1.4em]Solution

• Identify the disk:

  # ioscan -mdsf /dev/rdisk/disk69 Persistent DSF           Legacy DSF(s)========================================/dev/rdisk/disk69        /dev/rdsk/c7t2d4                         /dev/rdsk/c5t2d4

• Use the scsimgr utility to check the load balancing policy:

  # scsimgr get_attr -D /dev/rdisk/disk69 -a load_bal_policy
          SCSI ATTRIBUTES FOR LUN : /dev/rdisk/disk69
  name = load_bal_policycurrent = least_cmd_load  <---------------------  Exisiting Policydefault = least_cmd_load saved =

• To change the load balancing policy, use:

  # scsimgr set_attr -D /dev/rdisk/disk69 -a load_bal_policy=round_robinValue of attribute load_bal_policy set successfully

  NOTE:

  Valid options are: least_cmd_load Directs I/O requests through the hardware path with the least outstanding I/O requests. round_robin Cycles I/O requests through the available hardware paths in round robin fashion. cl_round_robin Cycles I/O requests through the available hardware paths in round robin fashion, within the locality of the CPU on which the I/O was initiated. This is known as cell-aware round robin. weighted_rr Cycles I/O requests through the available hardware paths in round robin fashion, subject to a user-assigned weight for each path. A hardware path is used until the number of I/O requests matches its weight , and then another path is chosen. preferred_path Directs I/O requests to the specified hardware path, if available. pref_tport Directs I/O requests to the specified target port, if available. closest_path Directs I/O requests through the hardware path with the lowest memory access latency, based on its affinity with the CPU processing the I/O operation. path_lockdown Directs I/O requests through a single hardware path. The chosen hardware path is the one that is least loaded when the device is opened. This algorithm is the only one supported for serial devices such as tape drives, changers, and SCSI controller devices, and does not apply to block devices such as disks.