how to change the reserve_policy so that multiple IBM VIO servers can access the same disk

In a p5 environment, for disk redundancy through two VIO servers, the default reserve policy on the disk needs to be changed to "no_reserve". This allows multiple VIO servers to see the disk and provide redundancy to LPARs. Here is the command:

# chdev -l hdisk# -a reserve_policy=no_reserve -P

This requires that the disk be removed from the system and brought back in. This can be accomplished with a reboot, or the following commands:

1. unmount and vary off the VG that the disk is part of.
2. rmdev -l hdisk#
3. mkdev -l hdisk#

NOTE: The "-P" makes the change in the ODM. Without it, the command will not work because it tries to update the disk while it is already configured in the sytem and an error will be reported. That is why the removal and restoration of the disk is required.

Example:

chdev -l hdisk3 -a reserve_policy=no_reserve -P