RE: [Xen-users] Live migration not permanent?

["Ross S. W. Walker" <rwalker@xxxxxxxxxxxxx>]

Jeff Lane wrote:

> On Fri, May 16, 2008 at 6:38 PM, [STD]Ein <ein@xxxxxxxxxxxxxx> wrote:
> > It is the expected behaviour.  It's your responsibility to ensure that the
> > domain isn't started on more than one host at a time (this may be enforced
> > by your shared storage solution).
> 
> Yep.  The only thing live migration does is move the running domU from
> its current memory location on Host A, to a new memory location in
> Host B.  It does not move any config files, and you MUST use shared
> storage to have a working domU on Host B after migration.  You CAN
> migrate a domain that has storage local to Host A but not Host B,
> however, what happens is that on Host B, you get a running guest that
> can not access its filesystem, and much hilarity ensues when you try
> to do anything that involves accessing the filesystem.
> 
> So, the requirements are:
> 
> Host A --|
>           ----- Shared Storage (I use Fiberchannel storage for this)
> Host B --|
>
> And, if you want to permenantly move the domU from host A to host B,
> you need to move the domU config file from hostA to hostB as well.
> 
> Also, you could have Host A be a mirror of Host B (failover scenario)
> so if Host A bites the dust, you can run the domU to your heart's
> content on Host B, since B has the config file too...
> 
> YMMV, of course...

Now I believe if you add your domU to the xenstore with 'xm new <config>'
and work completely out of the xenstore then after migration the domU
in the xenstore will be in Host B and not Host A so there should be
no chance of starting a duplicate unless you do a 'xm create <config>'.

-Ross

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