High availability on two boxes

[Uno Engborg]

Hi,
I'm experimenting with a HA setup on two physical boxes.  The idea is to 
create virtual Xen machines that  automagically do live migration from 
one physical box to the other in case of e.g. a hardware failure on one 
of the physial boxes.

My idea is to create a software raid of networked block devices and real 
disks.  I.e:

Box A:
Software raid consisting of:
Physical disk in box A
Nework block device exported from box B

Box B:
Software raid consisting of:
Physical disk in box B
Network block device exported from box A


On top of this I plan t use  GFS2 and a cluster that handles the 
migration of the virtual machines.

Any comments on this, would this work, or would it result in deadlock? 
What about quorum disk? I suppose
I need one? Most setup of these kind of things usually have their 
storage on a separate
SAN, but as this is mostly for experimentation and testing purposes, I 
would hope that I could do without that for now.

What would be the best way to export the network block devices? I'm 
thinking iSCSI or GNDB?

If this doesn't  look like a good idea, are there any other way to do this.

Regards
Uno Engborg