Re: [Xen-users] Re: Access Hypervisor Control from DomU

[Nils Toedtmann <xen-users@xxxxxxxxxxxxxxxxxx>]

Moin!

Am Dienstag, den 04.04.2006, 13:28 -0400 schrieb Stephen C. Tweedie:
> On Fri, 2006-03-31 at 13:59 +0200, Nils Toedtmann wrote:
> > > if this would be a problem you would have to deal with in the
> > > real world, you would have a identical box on another location and move
> > > the domU's to it and reboot the problem box.
> > 
> > But that is the exact problem: afaik you cannot move domUs or reboot the
> > "problem box" remotely if dom0 userland is dead! You are locked. 
> 
> Serial console is your friend. :-)
> 
> Not only does it give you a ttyS0 login to the dom0 even if networking
> is down; it also gives you a reliable way of capturing log information
> so you know just how dead the dom0 really is.  
[...]

True, much better solution! But unfortunately, our situation is like
this:

> Of course, with hosted services you might not be able to set this up

We have only one colo box. Even if we had two boxes, we would not place
them in the same rack (sharing switch, UPS & cooling). Since some ISPs
like to screw up their BGB sessions, we maybe would even prefer placing
them at different ISPs (using "loose" fallback mechs like rsync) over
having Gbit-connection/heartbeat/DRDB.

So we need at least four boxes: two HA-pairs, sitting in different
BGP-AS', each HA-pair interconnected via crossover-Gbit (for DRDB) and
three serials (on for heartbeat, two for ttyS0 in both directions). Btw,
do you have 10k$ you'd like to give away?

A "fallback dom0" would be a poor man's last resort.

/nils.


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