Have a pool of 3 servers. All are Xen v6.2. Applied latest patches this morning in the usual fashion:

  • Patch pool master
  • Move VMs off of slave machine 1 and restart it
  • Repeat with slave 2 and then master

This has worked previously.

This morning the first slave won't come out of maintenance mode. Have attempted multiple reboots, 'restart toolstack' and even removing it from the pool. Most report "Cannot forward messages because the server cannot be contacted. The server may be switched off or there may be a network connectivity problem."

I know this isn't the case as I can SSH to the machine from elsewhere in the subnet.

Suggestions as to where I went wrong and how to fix this?


You should restart the MASTER first, then the slaves. This has been the recommended sequence for as long as I can remember.

  1. Reboot the XenServer host. Reboot the pool master first. Do not place the pool master into maintenance mode because this designates another host to be the pool master. You will then have a slave with a higher version than the pool master. Recovery would involve reinstalling XenServer; there is not a rollback process for XenServer hotfixes.

Source: http://support.citrix.com/article/CTX132791

If you didn't put the original master into maintenance mode, then you might be able to get away with forcing the master to restart, then the slave will be able to talk to it again.

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