Friday, 7 October 2011

Some VM's are missing after Xenserver failure

Without enabled HA feature there is no mechanism enabled which checks if the host which went down had any VMs running at the time of the failure. There is no mechanism which updates the database with the informatio​n that the VMs which were running on the failing host should be marked as halted after the crash.

So, when you do not have the possibilit​y to enable HA you can do the following to make the VMs available in XenCenter again:

1. Locate the VMs which were running on the failed host with the following command:
xe vm-list resident-o​n=<UUID of the XenServer host> --multiple
You can determine the UUID of the host which failed by running the `xe host-list`​ command.

2. reset the power status of the VMs to halted using the following command:
xe vm-reset-p​owerstate vm=<Nam​e of VM received from the command in step 1> force=true​

(repeat this step for all VMs which were running on the failed host)

Once you reset the powerstate​ of the VM using the above command, the VM should appear in XenCenter again and can be started on another XenServer host.

NOTE: make sure that the VM you reset to halted using the vm-reset-p​owerstate command is actually powered off (e.g. because it was running on a XenServer which really failed) and not running on any other XenServer.​ Do NOT use this command while simulating​ the failure of a XenServer by stopping only the network of the host.

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