CentOS virt - Apr 2015 - Recommendations for virt on Opteron 275 systems.

Hello, CentOS-virt list.

The institution where I work has been donated some older IBM 
BladeCenters with IBM's LS-20 blade servers installed.  These LS-20's 
are equipped with Opteron 275 processors (dual-core, dual-socket).  In 
researching my virtualization options, I initially wanted to do oVirt, 
but after thoroughly investigating, it appears that oVirt, being based 
on KVM, will not work due to the Opteron 275 not supporting AMD-V 
virtualization extensions.

So, further investigation showed that Xen4CentOS, using 
paravirtualization, should be supportable.

So I'm looking for advice on deployment, including some pointers to some 
howtos or other documents on how to go about setting up a moderately 
large virtualization farm with Xen4CentOS on up to 200+ LS-20 blades, 
most of which have smallish internal storage, but with iSCSI 
connectivity to an EMC SAN; the deployment would start small and would 
grow as needed.  I'm looking for the ability to do HA-type things, live 
migration, etc, to replace an aging VMware ESX setup. Windows guests are 
not a requirement.  Pointers to solid VM management tools, especially 
for the HA and live migration options, would be nice.

Purchasing upgraded blade servers isn't really an option for us at this 
time.  (Now, if you or your organization wanted to donate some HS-21's 
or later, we would be glad to accept them; we are a 501(c)(3) 
not-for-profit public foundation...... :-)    and then I could run oVirt).