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Best MPIO Practices on VIOS


I'm setting up a 750 with Dual VIOS (full how-to to be compiled in a few
Each VIOS has 2 8GB Dual Port adapters, each port goes to a different
controller on the storage (i'm not savvy enough about Hitachi's VSP series,
but they dint seem to use the DSXXXX style of "preferred controller" so any
port is good).
I noticed i can change the path priorities on VIOS to make a rudimentary
balancing (since IBM i uses most arms at the same time, it's ok to do it
this way and not with round robin or some more advanced algorithm).
My question was (since i couldn't find it in most of the documentation I've
¿Is there any problem with changing the priority on the paths on certain
disks, for example even disks via fscsi0 and odd via fscsi1?
I cobbled together a nifty line that gets me the chpath command with
current priorities which i can use to change priorities to what i want (1
for the least used path, 255 for preferred).
I just tested it and it takes effect immediately and, since the paths are
still there, mpio should do the failovers without problem in case of fiber
or switch failure (i will try it, once i finish restoring the systems).
I know that there is no support for load balancing at the IBM i level, IBM
i just takes the first vscsi controller and directs all traffic there which
means that i have to alternate Load Source tagging between partitions but
since i didnt find anything against doing this manual load balancing AND
the vios commands allow me to do it (no oem_setup_env needed to do it) i
think it should be OK.
If anyone wants, the line is this:
lspath -field name status parent | grep fscsi | while read disk status
parent; do priority=`lspath -dev $disk -pdev $parent -lsattr -attr priority
| grep priority | awk '{print $2}'`; echo "chpath -dev $disk -pdev $parent
-attr priority=$priority"; done

I adapted it from an AIX blog and tailored for the vios syntaxis and output
This line only prints the commands that set all paths to the current
setting. Only copying the output, modifying and then pasting back would
change anything.

Best Regards,


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