How to move I/O path from primary to alternate link path

[Darius Shafie]

I have been reading the forum and researching commands to move I/O path from primary to alternate link and then back to primary again.

I have an issue with the I/O not failing over to the alternate link when the primary path fails. The filesystem is configured on a regular vg nothing special or out of the ordinary.

So far I've not been able to find a command that will enable me to manually move the I/O path.

Does anyone know which command to use?

Kindest Regards.

[Geoff Wild]

vgreduce /dev/vgXX /dev/dsk/cXtXdX

then vgextend it back in.

Rgds...Geoff

[Juan M Leon]

can you post a vgdisplay -v
I would like to see the information for the volume groups. it should fail over the laternate path if it is configured.

[Torsten. · Accepted solution]

For a not permanent change use pvchange -s:

http://docs.hp.com/en/B2355-60105/pvchange.1M.html

"For multiported devices accessed via multiple paths, pvchange may be used to customize the circumstances that may cause LVM to automatically switch from one path to another, or when LVM will switch back to a prior path which failed when it is available again (generally described as the physical volume's autoswitch behavior). pvchange also permits you to switch manually to a specific path to the physical volume."

Manually switch a physical volume to use another controller path:

pvchange -s /dev/dsk/c2t0d2

Did you wait for the timeout?
Is autoswitch set to on?
Is the path healthy?

[D Block 2]

run both:

# ioscan -kfnC disk

# vgdisplay -v

as Juan Leon mentioned above. We are now on the same page. For example, what is..

a) are these links for vg00 or other ?

b) how many alternate links are there ?

c) what is the active or primary link to fail ?

d) I'll assume this is nothing to do with the boot disk, correct ?

Testing - a method:
if the Primary is on an external disk, then pull the Fibre Cable out and look at the system log, do you see any errors ? failover to alternate ? **WARNING** do not attempt this unless you have the pvlinks setup properly for all disks on this Hardware Path !!!

now put back the fibre connection or cable, was there any recovering messages in the log file ?

Also, what is your TimeOut values (see pvchange -t for timeout in seconds) ? 60 seconds ? so, when you pull out the cable, you must wait for a period for the Timeout.
Assuming there is an I/O request on the Link (primary path) and the timeout is reached, then the path should also fail over to the alternate path to handle the i/o request.


put back the fiber cable, and see the system log, did the PV recover back to the primary ?

[Nguyen Anh Tien]

To make an alternate link become the primary link (manual switch) use pvchange:
# pvchange -s
HTH

[Juan M Leon]

I agree with Geoff, to make a permanent change from alternate to primary use vgreduce and vgextend.

But If you want to switch for a short time you can use pvchange -s. Remeber pvchange only helps to move the paths from the primary to alternate, but does not configured or set permanently.

hope it helps.

Thank you

Juan

[Juan M Leon]

Darius,
Hello, hope you have find your answer.
would you mind assigning some points.
Thank you

[Darius Shafie]

In the end I corrected and reconfigured my SAN, so this no longer was an issue.