Monthly Archives: March 2012

Change EMC Powerpath Failover Policy on UNIX Systems

As UNIX system administrators – we need our Operating Systems running in optimal state every time. The same is what we want to our storage systems. In EMC Powerpath there are a couple of failover policies that we can enforce to our storage devices but we must always use the one that is best suitable. We have here a LUN that is currently under Basic Failover policy even though the storage is CLARiiON:

[email protected]#  powermt display dev=emcpower1a
Pseudo name=emcpower1a
CLARiiON ID=APM00012345678 [solaris/polaris]
Logical device ID=60060160EABCDEFGHIJKL00MNOPQRS12 [LUN 155]
state=alive; policy=BasicFailover; priority=0; queued-IOs=0
Owner: default=SP B, current=SP B
==============================================================================
---------------- Host ---------------   - Stor -   -- I/O Path -  -- Stats ---
### HW Path                 I/O Paths    Interf.   Mode    State  Q-IOs Errors
==============================================================================
2304 [email protected][email protected] c3t0d1s0  SP A3     active  alive      0      1
2304 [email protected][email protected] c3t1d1s0  SP B3     active  alive      0      0
2305 [email protected][email protected] c4t0d1s0  SP B1     active  alive      0      0
2305 [email protected][email protected] c4t1d1s0  SP A1     active  alive      0      1

To fix this issue – we need to set the failover policy back to CLARiiON:

[email protected]#  powermt set policy=co dev=emcpower1a

[email protected]#  powermt display dev=emcpower1a
Pseudo name=emcpower1a
CLARiiON ID=APM00012345678 [solaris/polaris]
Logical device ID=60060160EABCDEFGHIJKL00MNOPQRS12 [LUN 155]
state=alive; policy=CLAROpt; priority=0; queued-IOs=0
Owner: default=SP B, current=SP B
==============================================================================
---------------- Host ---------------   - Stor -   -- I/O Path -  -- Stats ---
### HW Path                 I/O Paths    Interf.   Mode    State  Q-IOs Errors
==============================================================================
2304 [email protected][email protected] c3t0d1s0  SP A3     active  alive      0      1
2304 [email protected][email protected] c3t1d1s0  SP B3     active  alive      0      0
2305 [email protected][email protected] c4t0d1s0  SP B1     active  alive      0      0
2305 [email protected][email protected] c4t1d1s0  SP A1     active  alive      0      1

Here are the other policies that you can use to set the correct one for your storage array:

powermt set policy=rr|io|lb|so [dev=power#|all]

The dev parameter is optional. If you do not include the dev parameter,
the powermt set policy command changes the policy of all PowerPath devices.

Parameters
· so = Symmetrix Optimization (default)
· co = Clariion Optimization
· li = Least I/Os (queued)
· lb = Least Blocks (queued)
· rr = Round Robin (one path after another)
· re = Request (failover only)
· nr = No Redirect (no load-balancing or failover)