Saturday, 7 September 2013

XenServer Multipath Issues

I would like to elaborate some simple techniques for one Multipath issue on ISCSI storage very often bogging the enterprise.

Some paths not available to newly added hosts :- This is very common issue. A host is added in the pool and instead of locating all the paths to a storage, it has started to see only a few path.

*) A first point of troubleshooting is to check if you are able to ping all the ip's of the storage.
*)Next check for the multipath status.
multipath -ll
You could go for a forward troubleshooting technique :-
manually discover each of the node :- 
service open-iscsi restart
# iscsiadm –m discovery --sendtargets –portal <ip_addr_of_storage>
Note:- The storage IP for each of the controller should be in different network. This could be a probable reason why XenServer fails to connect to the controller as the network was not configured to connect to the network. Always check for the network settings for storage in XenServer network tab.

Then log on to all the nodes of the storage at one shot by :-
#iscsiadm -m node -L all

Or log on to each of the node separately by :-
# iscsiadm –m node –T –p <ip-address-of-the-storage> -l

and then 

Give the server a reboot, if this doesn't resolve the issue.

If the above technique fails you could probably go for a reverse engineering technique :-

logoff all the targets:-
iscsiadm -m node -u all

shut the iscsi service down by either of the command :- 
chkconfig open-iscsi stop
service open-iscsi stop

Change the multipath status of the host to inactive and then reboot.

Re-initialize the multipath configuration on the host.

I hope this article will definitely come handy when facing issues like this one.