Aug 18, 2019 - 09:00 PM
It depends on how your estate is configured. Are you referring to a scenario where you have production instances of Red Hat VMs being live migrated between ESX hosts? If you are, then you don't need the HA add-on subscription. In this scenario, there are two common ways to purchase subscriptions for RHEL:
1) Buy Red Hat Enterprise Linux Server subscriptions using the physical or virtual nodes metric. Each one of these allows you to run RHEL on 2 x VMs for each subscription. There are no rules around where said VMs can be hosted in your environment or live migration. So, if you have 100 VMs running RHEL, you would need 50 subscriptions. It's that simple.
2) Buy Red Hat Enterprise Linux for Virtual Datacenter subscriptions. The metric here is a "socket-pair" of physical CPUs, so each subscription covers 2. This subscription is applied to the socket CPUs of the ESX host servers and allows for unlimited virtualisation on that server. They are also stackable, so if your host server has 4 x socket CPUs, you can apply 2 subscriptions to it.
So, if this is what you are asking, the next question is how dense is your virtualisation? If you have Red Hat VMs hosted across your virtual environment in lots of different clusters, go for option 1. If you have heavy concentrations of virtualisation in certain clusters, option 2 is probably your best option. The break point is approx 7 VMs - if you have 7 or more RHEL VMs per ESX host, option 2 is cheaper.
The HA Add-On is actually for active / passive clustering of RHEL servers,whether they be physical or virtual, to allow for failing over of services from an active node to a passive node.
Aug 19, 2019 - 06:38 PM
Thanks a lot for the detailed explanation.
Yes, i was referring to production instances of Red Hat VMs being live migrated between VMware ESXi hosts.
We have proposed the same approach for assigning Red Hat Enterprise Linux subscriptions in a virtualized environment, taking into consideration the cost factor.
I was particularly interested in understanding the scenarios in which "High Availability Add-on" subscriptions will be applicable - Thanks for the clarification.