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Re: Best MPIO Practices on VIOS



fixed

Didn't get to pull the cable, client didn't want to stay for still more
overtime...
I'll try it on my test system back at the lab and append the conclusions to
the how-to.




On Sun, Dec 8, 2013 at 9:35 AM, Roberto José Etcheverry Romero <
yggdrasil.raiker@xxxxxxxxx> wrote:

It shouldn't. The last restore is finishing it's run, when it does i'll
test unplugging one of the two paths, since both paths are enabled in the
aixpcm it should gracefully failover.


On Sun, Dec 8, 2013 at 6:56 AM, Jack Kingsley <iseriesflorida@xxxxxxxxx>wrote:

How does doing this effect mult-pathing.


On Sat, Dec 7, 2013 at 9:51 PM, Roberto José Etcheverry Romero <
yggdrasil.raiker@xxxxxxxxx> wrote:

No, i mean:
VIOS usually directs ALL IO activity thru the first path that it finds
(unless SDDPCM or something like that is installed and controller
preference is in order).
In this case i first had ALL io going thru the fscsi0 port. After a VIOS
reboot i saw some luns going out the fscsi1 port even though priority
still
was set as 1 and 1 in each path (VIOS must have seen fscsi1 path first
during initialization).
After doing the aforementioned changes in priority (even disks now have
255
as priority on the fscsi1 path and odd disks the same but for the fscsi0
path).
I now see balanced IO and better than before, since more FC and
controller
ports are in use (during disk initialization i saw a limit of around
400Mb/s and 8k IOPS per port, in fact it was then that i noticed all
this
since 11 luns were on one port and 6 were on the other. the 6 finished a
lot earlier than the 11).
Ah, in case someone is wondering, the topas command brings all this
data,
remember to change the mode with D and d to see both per disk and per
parent data.
Best Regards,



On Sat, Dec 7, 2013 at 10:30 PM, Jack Kingsley <
iseriesflorida@xxxxxxxxx
wrote:

Roberto, can you define: rudimentary balancing, are you referring to
some
sort of load balancing within the Hitachi SAN.


On Sat, Dec 7, 2013 at 7:49 PM, Roberto José Etcheverry Romero <
yggdrasil.raiker@xxxxxxxxx> wrote:

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

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