DR planning: Managing vSphere licenses if a host needs to be replaced
Whilst writing some DR plans for our VMware cluster, I became aware of my lack of knowledge in how vSphere licenses are managed.
I have 3x ESXi 4.0 hosts and a single vCenter server. All of the ESXi hosts boot from embedded (removable) USB keys. If one of these servers suffers a catastrophic hardware failure and needs to be replaced, what is best procedure to get up and running quickly on new hardware?
Is it possible to remove the USB stick from the dead server, install it in the replacement hardware, power on and continue working? Or is there some connection made when the the license is attached to the server linking with the MAC address or CPU ID, or with a certificate or ssh key? Will there be any problems with the new hardware coming online with the same name but different MAC addresses?
Secondly, if the USB key in the server also died, and i need to replace the whole server including the USB stick, I would boot from CD and install the latest ESXi 4.0 version to a new USB key. What is the recommended procedure for adding that server to the cluster? Do i need to remove the old server first, and then add the new one?
The server-based licenses are assigned when the host is connected (i.e. the "Add host" wizard) to the vCenter and as long as the host remains in the list of hosts, it will also occupy a license (unless you manually assign it another or chose Evaluation Mode of course). If a host dies for some reason, disconnect and remove it from vCenter, replace/reinstall and then connect it again.
As for moving USB keys from one server to another, I can't say for sure but if the hardware is identical there should be no problem. You should try this out when doing a dry DR run, the best way to revise it is to try it.