XenServer - MPIO

Virtualization is a real hot topic as we all know but unless you do it right you can cause yourself a lot of grief that is all to real.

Using XenServer's native support for ISCSI you can have yourself a nice little robust virtual environment, with the use of Shared Resources if any hardware goes down you are but a click away to recovery (XenMotion).
Dell's EqualLogic PS5000 Series


That is unless that hardware is your one and only NIC!

There is always an answer to IT woes however, and MPIO or Multipath for XenServer is the answer to NIC issues. Citrix's XenServer does natively support ISCSI but to get the Multipath to work it takes additional configurations, and I will help shine some light on this with some undisclosed documentation.

What you need:

1. NIC for your XenCenter Management
2. Redundant NICs for your ISCSI Data
3. Some CLI experience

On your XenCenter Console open the following file using your favorite CLI editor

/etc/iscsi/iscsid.conf

Add a comment code out the line node.startup = manual
Remove the comment code to the line node.start = automatic
Save this file

Run the following commands to set the services (daemon) to start on startup
chkconfig open-iscsi on
chkconfig multipathd on

Next you will need to edit the following file:

/etc/multipath.conf
Add line under defaults {
path_checker readsector0
rr_min_io 100
Save this file

Run the service start commands
service open-iscsi start
service multipathd start

Run the following ISCSI discovery commands
Iscsiadm –m discovery –t st –p ipaddress of ISCSI device
Iscsiadm –m node –L all
multipath -l

*Noted the results for your wwid fields, yes it is a really long number

Open the following file
/etc/multipath.conf
Add iscsi device(s)
multipaths {
multipath{
wwid %multipath -l%
alias %friendlyname%
}
multipath{
wwid %multipath -l%
alias %friendlyname%
}

Save this file
Run the following command to confirm success
ls /dev/mapper