Re: Best MPIO Practices on VIOS

[Roberto José Etcheverry Romero <yggdrasil.raiker@xxxxxxxxx>]

Sigh, where it says 2 8GB Dual Port adapters, it should say 1 8GB Dual Port
adapter. only 1 per vios....


On Sat, Dec 7, 2013 at 9:46 PM, Roberto José Etcheverry Romero <
yggdrasil.raiker@xxxxxxxxx> wrote:

> I'm setting up a 750 with Dual VIOS (full how-to to be compiled in a few
> weeks).
> 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 read):
> ¿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.
> Thoughts?
> 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,
>
> Roberto