Re: XEN and failover

Re: XEN and failover

[Thorolf Godawa]

Hi,

 >First off, please don't reply to some random thread if you indend
 >to open a new one.
sorry for this, I just was to lasy, I take care not to do it again.

OK, I have the following:

Two servers connected via NFS to a storage-solution.

Both servers have the same hardware and same software (SLES 10.0b3) on 
it, both are running XEN 3.0.0 and some Linux-guests for testing.

I'm able to do "xm save/restore", "xm migrate --live ..." etc.

 >Then, for failover, I don't see a reason why you shouldn't be able to
 >apply the normal linux failover solutions to xen domUs, like heartbeat
OK, but heartbeat just checks if the other machine is still there and 
then it can do s.th., f.ex. starting the domU that just crashed on the 
master machine on the backup machine!

But it would be better to make in an fixed (and short as possible) 
interval snapshots of the running VM including processor and memory 
(like "xm save" does, but without interrupting or even disturbing the VM 
too much), putting it on the shared storage and if the domU crashes 
restoring it from the backup host quite fast and in a most actual state!

I've read several times the XEN 3 should support failover with the 
live-migration, but how can I use it for the BEFORE the master crashes?

 >The main problem with failover solutions always is to make sure the
 >failing host releases its MAC or IP. Solutions include disabling the
With XEN 3 and the live-migration this should not be a big problem, or?

 >failover solutions usually provide means to execute a script whenever
 >action is needed, so issuing the right commands to your dom0 should be
 >quite easy.
Yes, it should be, but only if you know the right commands and there 
parameters :-)


Thanks for your answers,
-- 

Chau y hasta luego,

Thorolf

Re: Re: XEN and failover

[Thorolf Godawa]

Hi all,

where do I find more information about the following:

xc_save xcfd iofd domid maxit maxf flags
xc_restore xcfd iofd domid nr_pfns store_evtchn console_evtchn

What are the commands doing exactly and how are they doing it, what do 
the parameters mean exactly?

Is it possible to realise a failover with this, can xc_save make 
snap-shots of a currently running VM without disturbing it much so if 
this host/guest crashes can I restore it quickly with the most actual 
status?

Thanks a lot for your help,
-- 

Chau y hasta luego,

Thorolf