Azure Stack regularly releases updates, typically monthly. Sometimes in those updates we find good feature additions, bug fixes, and other items. Sometimes we see a bit of the ugly of cloud in known issues or workaround. In this particular update there is one point that stands out above the rest as being a little odd:
This is one of those ugly ones, and is caused by stability issues at high VM counts we’re told. So basically they’ve added a new limit on the number of VMs per node (60) and the number of VMs per solution (700, or 11.6 nodes at 60 per node). Now whats weird about this is its a VM limit. Not a vCPU, not a RAM, not a disk or other hard resource limit, but rather a VM. This means any calculations you do for capacity on Azure Stack need to take this new limit into consideration. Don’t simply assume that adding nodes will allow you to add more VM capacity if your already at these limits, even if your not at the 16 node limit yet.
I can certainly attest to some stability issues with high numbers of VMs accross large numbers of nodes, so it makes sense, but it bears repeating: Always read the release notes!