Similar to the parallel policy, but rather than checking the primary first, reads are  alternated between all copies. With AIX 7.1.03.05, a new option was introduced for AIX LVM that allows a preferred read to  be set to one copy of the logical volume. This flag ( -R ) is used with mirror pools and setting  the value 1 - 3 to specify the preferred mirror pool. Setting the value to 0 disables the  preferred read copy. Note:  Setting the preferred read copy overrides the scheduling policy while the preferred  copy is available. If it is not available, the reads follow the scheduling policy for the logical  volume. With PowerHA V7.2.3, the Cluster Single Point of Control (C-SPOC) SMIT menus were  modified to include the preferred read option so that logical volumes can be configured at the  cluster level with mirror pools and a preferred read set. Note:  Some problems were found with the implementation of this change during the  testing for this IBM Redbooks publication. Check the readme file for details about the fix  that is available in the Version 7.2.3 SP1 release. Chapter 2. New features  49