Citrix Systems 6 User Manual

104

If the master is really dead, choose one of the members and run the command xe pool-emergency-transition-
to-master on it. Once it has become the master, run the command  xe pool-recover-slaves  and the members
will now point to the new master.

If you repair or replace the server that was the original master, you can simply bring it up, install the XenServer
host software, and add it to the pool. Since the XenServer hosts in the pool are enforced to be homogeneous,
there is no real need to make the replaced server the master.

When a member XenServer host is transitioned to being a master, you should also check that the default pool
storage repository is set to an appropriate value. This can be done using the  xe pool-param-list  command and
verifying that the 

 parameter is pointing to a valid storage repository.

In the unfortunate event that your entire resource pool fails, you will need to recreate the pool database from
scratch. Be sure to regularly back up your pool-metadata using the xe pool-dump-database CLI command (see

1.

Install a fresh set of hosts. Do not pool them up at this stage.

2.

For the host nominated as the master, restore the pool database from your backup using the  xe pool-
restore-database  (see 

) command.

3.

Connect to the master host using XenCenter and ensure that all your shared storage and VMs are available
again.

4.

Perform a pool join operation on the remaining freshly installed member hosts, and start up your VMs on
the appropriate hosts.

If the physical host machine is operational but the software or host configuration is corrupted:

1.

Run the command:

            xe host-restore host=

<host>

 file-name=

<hostbackup>

          

2.

Reboot to the host installation CD and select Restore from backup.

If the physical host machine has failed, use the appropriate procedure listed below to recover.

Any VMs which were running on a previous member (or the previous host) which has failed
will still be marked as 

Running

 in the database. This is for safety-- simultaneously starting

a VM on two different hosts would lead to severe disk corruption. If you are sure that the
machines (and VMs) are offline you can reset the VM power state to 

Halted

:

xe vm-reset-powerstate vm=

<vm_uuid>

 --force

VMs can then be restarted using XenCenter or the CLI.

1.

Run the commands: