Accessing a LUN across a partner path will function fine
... and in some cases, there may be no problems perceived.
However, IOs across the the partner path do not perform
as well under load than access to the primary
paths.
For
ESX, proper path prioritization is very easy to accomplish with the scripts
provided in the Host Utilities Kit.
As for the original issue on this thread ... assuming
you have multipathing set up correctly, the warning may be associated with
normal path checking activity.
Check your lun stats data and divide the "partner kb"
by "partner ops", if the answer there is ~512b ... then these warnings could
simply be path checking done by multipathd.
If the average IO size seems significant, open a case
with support and get some assistance in determining why IO is going over the
partner path.
--
errol
I'm a little foggy on the details... it's been a while since I read them or
thought about it. But, assuming you mean single_image mode, host can see
the luns on all four ports, and data can be accessed through all four
ports. Now N1 may own the lun, but it can be accessed "through the
interconnect" through N2.
Multipathing on the host determines which path
will be used to access data, and whether or not the an active/passive or round
robin (or whatever). If you are using Netapp multipathing, it knows to use
only the N1 path. But other multipathing doesn't understand this, and will
pick the primary path at random.
I have tons of VMWare hosts that have
seemless esx multipathing, but pick the wrong paths by themselves. Then
you get the error. I get this error all the time and really haven't had a
problem with it... but it's the first thing support will bring up when you call
about anything. I have noticed that it seems to run the CPU a little high
(since it has to swap things in and out of memory through the
interconnect).
Fred
From: Linux Admin
<sysadmin.linux@gmail.com>
To: NetApp Toasters List
<toasters@mathworks.com>
Sent: Wednesday, March 4, 2009 2:38:19
PM
Subject: FCP Partner Path
Misconfigured - Host I/O access through a non-primary and non-optimal path was
detected.
Hello Toasters.
I am receiving the following
message from auto support: FCP Partner Path Misconfigured - Host I/O access
through a non-primary and non-optimal path was detected.
I have a single
cluster acting in single fabric mode and it is wired up in the following
way.
Each host has an i-group on each node of the cluster for. Each of the
netapp node is connected to sw1 and sw2 and hosts also has a path to sw1 and
sw2.
Why would the host access luns on N2 via partner node
N1
---------------
---------------
{
n1 }
{ n2 }
| \
/ |
|
\
/
|
| \
/
|
| \
/
|
---------------
---------------
{ s1
} {
s2 }
\
/
\
/
---------------
{ host
}