[Linux-cluster] virtualized guest failback

[John Ruemker]

Stepan Kadlec wrote:
> Hi,
> I have working failover of virtualized guest. could someone give me 
> hint how to configure the vm failover to failback after recovery? eg. 
> vm_A runs xen01, xen01 fails, so xen02 takes over the vm_A, after 
> xen01 is up again, the vm_A is migrated back to xen01.
>
> I have already tried many config combinations, but without success - 
> the vm_A always stays on the failover host.
>
> my expected config (which still doesn't work) is:
>
>  <rm>
>     <failoverdomains>
>       <failoverdomain name="xen01" restricted="1" ordered="1">
>         <failoverdomainnode name="xen01.localdom" priority="2"/>
>         <failoverdomainnode name="xen02.localdom" priority="1"/>
>       </failoverdomain>
>       <failoverdomain name="xen02" restricted="1" ordered="1">
>         <failoverdomainnode name="xen01.localdom" priority="1"/>
>         <failoverdomainnode name="xen02.localdom" priority="2"/>
>       </failoverdomain>
>     </failoverdomains>
>     <resources/>
>
>     <vm autostart="1" domain="xen01" exclusive="0" migrate="live" 
> name="vm_A" path="/etc/xen/vm" recovery="relocate"/>
>     <vm autostart="1" domain="xen02" exclusive="0" migrate="live" 
> name="vm_B" path="/etc/xen/vm" recovery="relocate"/>
>   </rm>
>
> any hints? thanks stepan


Your failoverdomains are setup to allow that, but it looks like you have 
your priorities switched.  Domain xen01 prefers xen02.localdom and 
domain xen02 prefers xen01.localdom, since the lowest priority score in 
a domain is preferred.  So since vm_A is in xen01 it will choose to 
start the guest on xen02.localdom.  If that node fails it will move to 
xen01.localdom, and will fail back to xen02.localdom if that node 
returns.  Switch the priorities in each domain and you should have the 
behavior you want


      <failoverdomain name="xen01" restricted="1" ordered="1">
        <failoverdomainnode name="xen01.localdom" priority="1"/>
        <failoverdomainnode name="xen02.localdom" priority="2"/>
      </failoverdomain>
      <failoverdomain name="xen02" restricted="1" ordered="1">
        <failoverdomainnode name="xen01.localdom" priority="2"/>
        <failoverdomainnode name="xen02.localdom" priority="1"/>
      </failoverdomain>


-John