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Licensing Hyper-Converged Architectures

David Klee discusses SQL Server licensing on a unique (but growing in popularity) hardware architecture:

Now, look at the hyper-converged architectures. The CPUs used for I/O handling are the same as those that your VMs use to power your applications. A substantial portion of the host’s CPU power is now needed for I/O handling, and this activity comes first in the CPU scheduling queues.

This fact, by itself, is not necessarily a problem. Most virtualization host CPUs are relatively lightly utilized, and this amount of CPU needed for I/O handling is readily absorbed without causing a performance problem.

But, larger scale SQL Servers can read and write exceptionally large amounts of data around the clock. The I/O handling at the host layer can start to drain resources from the host. The additional activity scheduling time inside the hypervisor could be slowing down these SQL Servers without you knowing it.

As always, work out how your licensing would look under different alternatives or you could end up wasting a pretty penny.