Load balance policy change in HP UX : How to ??

1. Identify the disk:

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

2.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_policy
current = least_cmd_load  <---------------------  Exisiting Policy
default = least_cmd_load saved =

3.To change the load balancing policy, use:

# scsimgr set_attr -D /dev/rdisk/disk69 -a load_bal_policy=round_robin

Value of attribute load_bal_policy set successfully

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.

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