Do there exist any open-source solutions? Perhaps, cheaper commercial ones?
I'm surprised that googling does not yield anything meaningful for me.
Ah - no. Windows HPC allows you to use the very cheap WIndows HPC edition licenses. If you take naother management - and need windows - it is back to standard edition windows, which costs a LOT more than the node cost of HPC cluster. The result of a zero costs solution would thus be still MORE expensive than the MS HPC cost. That is, if you really need a HPC cluster and was not mixing that up with MS "standard" clustering, in which case, though, teh same logic applies - management services cost zero and are included in the actual licenses.