On our testing, XenServer is the best virtualization package currently available. The management tool (XenCenter) is pretty much as good as VMware's VirtualCenter, and anyone from an ESX server background will feel right at home. The big difference is that XenServer runs on pretty much any hardware (because underneath it just uses the Linux dom0 instance for drivers). By comparison, the VMware ESX server Hardware Compatibility List is pretty bare, and will only run on specific machines from the big hardware vendors.
Anyway, this post is about RHEL subscriptions and licensing. I submitted the following in a support case to Red Hat:
Case Title : Virtual instance licensing on non RHEL hypervisors
We've got a Citrix XenServer deployment to which we are looking to migrate some RHEL servers to. How do RHEL subscriptions work with non Red Hat shipped hypervisors (ie. VMware, Citrix, Hyper-V, etc.)?
1. Can I purchase Advanced Server subscriptions per-node?
2. Can I purchase Basic subscriptions for nodes with 4 or less RHEL VMs?
3. Or is it "per VM" if we're not running a Red Hat badged hypervisor?
I can't find anything on redhat.com about this. I assume it's #1 and #2, given this is what Novell / SuSE do (http://www.novell.com/products/server/virtualization.html). "one subscription to SUSE Linux Enterprise Server covers all virtual images on the same physical server".
Assuming this is the case, how do I go about registering the VMs with RHN?
In response, I got the following
Welcome to Red Hat support .
Since you are using Citrix XenServer deployment each of the virtual machine will be considered as a separate physical machine and you will have to purchase subscriptions for each virtual machine .
If you are using rhel vitalization you can have a single subscription and register unlimited guests .
Red Hat Enterprise Linux server subscriptions provide support for up to four virtualized guest environments.
For more details you can check this link
But since this is a third party vitalization you will need subscription for each virtual machine .
So, if you're using a competing virtualization technology, you pay per VM. The difference in costs is huge - if you're running several virtual machines per physical machine, you'll pay several times as much to Red Hat. Time to start looking at Novell's SuSE Linux Enterprise Server or Ubuntu again.