Originally posted by: klaasvaak

To test AIX 5.3 mpio capabilities, we are using the AIX 5.3 MPIO drivers to multipath-IO EMC Symmetrix disks, connected through fiber adapters.

1. lsdev -Cc disk

hdisk2 Available 0E-08-01 MPIO Other FC SCSI Disk Drive
hdisk3 Available 0E-08-01 MPIO Other FC SCSI Disk Drive
hdisk4 Available 0E-08-01 MPIO Other FC SCSI Disk Drive

1. lslpp -l mpio

devices.common.IBM.mpio.rte 5.3.0.32 COMMITTED MPIO Disk Path Control Module

Everything works ok, failovers, failback to the original path, booting from these devices with only 1 fiber connected etc.

The only thing I can't get to work is round_robin scheduling algorithm.

According to lsattr fail_over and round_robin are both valid:

1. lsattr -R -l hdisk3 -a algorithm

fail_over
round_robin

But changing it is not allowed?!?

1. chdev -l hdisk3 -a algorithm=round_robin

Method error (/usr/lib/methods/chgdisk):
0514-018 The values specified for the following attributes
are not valid:

The error message doesn't specify what it is that is not valid.
I haven't been able to come up with an explanation or a workaround, other than to install PowerPath, but I read that basic AIX MPIO should also be able to do round-robin.

What am I missing??

Regards,
Klaas


#AIX-Forum

Originally posted by: dimon

EMC requires installing the EMC ODM package when using Symmetrix disks on AIX, specifically the EMC.Symmetrix.fcp.MPIO.rte fileset if you want to use MPIO. I am not sure if this is the cause of the strange messages you are getting, but I suggest you try it out. The fileset provides its own PCM (path control module) that should support the round_robin algorithm. You can get the ODM package from ftp://ftp.emc.com/pub/elab/aix/ODM_DEFINITIONS
#AIX-Forum

Originally posted by: SystemAdmin

By default, AIX creates the MPIO hdisks with a reserve_policy set to single_path.
Visibly, and it sounds quite logical, this only allows for fail_over MPIO algorithm.

You have to specify a new reserve_policy in the chdev command:
chdev -l hdisk5 -areserve_policy=no_reserve -a algorithm=round_robin

Hope this helps.

Regards,
L.Esnoul

#AIX-Forum

Originally posted by: bodily

From what I have heard from others, to use EMC with MPIO you need to get the PCM (Path Control Module) from EMC to use it. Now I also heard that you could NOT use round robin that it was fallover only. I assume that has something to do with the PCM EMC provides. This is quite possibly of still getting revenue from PowerPath that provides round robin, when IBM provides multipath software for free either with the storage unit, or in the OS via MPIO>
#AIX-Forum