The I/O operation is distributed based on the path priority attribute. Paths that have a higher  path priority value receive a greater share of the I/O operations. Set the algorithm attribute to  round_robin  before you add the hdisk to any volume group. All  outgoing traffic is then spread evenly across all of the ports: chdev -l  <LUN>  -a algorithm=round_robin The  shortest_queue  algorithm is also available in AIX for FlashSystem. The algorithm is  similar to the  round_robin  algorithm. However, the  shortest_queue  algorithm distributes I/O  operations that are based on the number of pending I/O operations on each path.  The path that features the fewest pending I/O operations is selected for the next operation.  The path priority attribute is ignored when the algorithm is set to  shortest_queue . Therefore, if  one path is slow because of congestion in the SAN, the other less congested paths are used  for more of the I/O operations. The  shortest_queue  or  round_robin  enables the maximum  use of the SAN resources. To list the attributes of the LUN, enter the following command: The output of the  chdev  and the  lsattr  commands of the FlashSystem 900 that is used in  Example 6-1 on page 158 is shown in Example 6-3. The number of spaces in the output is  changed for clarity. lsattr -El  <LUN> Example 6-3 AIX chdev and lsattr commands # chdev -l hdisk4 -a algorithm=round_robin hdisk4 changed # lsattr -El hdisk4 PCM PCM/friend/fcpother Path Control Module False PR_key_value none Persistent Reserve Key Value True+ algorithm round_robin Algorithm True+ clr_q no Device CLEARS its Queue on error True dist_err_pcnt 0 Distributed Error Percentage True dist_tw_width 50 Distributed Error Sample Time True hcheck_cmd test_unit_rdy Health Check Command True+ hcheck_interval 60 Health Check Interval True+ hcheck_mode nonactive Health Check Mode True+ location Location Label True+ lun_id 0x0 Logical Unit Number ID False lun_reset_spt yes LUN Reset Supported True max_coalesce 0x40000 Maximum Coalesce Size True max_retry_delay 60 Maximum Quiesce Time True max_transfer 0x80000 Maximum TRANSFER Size True node_name 0x500507605efe0ad0 FC Node Name False pvid none Physical volume identifier False q_err yes Use QERR bit True q_type simple Queuing TYPE True queue_depth 64 Queue DEPTH True reassign_to 120 REASSIGN time out value True reserve_policy no_reserve Reserve Policy True+ rw_timeout 30 READ/WRITE time out value True scsi_id 0x10100 SCSI ID False start_timeout 60 START unit time out value True timeout_policy fail_path Timeout Policy True+ unique_id 54361IBM FlashSystem-9840041263a20412-0000-0004-00006410FlashSystem-984003IBMfcp Unique device identifier False ww_name 0x500507605e800e41 FC World Wide Name False Chapter 6. IBM FlashSystem 900 client host attachment and implementation  159