Different processor for same size VMSS

Question

We have Service Fabric application, that creates VMSS when we create the clusters. While creation we have to select the VM Size. We have 3 different regions where we have deployed our application.

Although the VM size selected is same for all 3 regions. The processor assigned is different. That's not a problem if the processors are similar in their performance. But it's not.

https://docs.microsoft.com/en-us/azure/virtual-machines/dv2-dsv2-series#dv2-series

Above link states:

Dv2-series sizes run on Intel® Xeon® Platinum 8272CL (Cascade Lake), Intel® Xeon® 8171M 2.1GHz (Skylake) or the the Intel® Xeon® E5-2673 v4 2.3 GHz (Broadwell) or the Intel® Xeon® E5-2673 v3 2.4 GHz (Haswell) processors with Intel Turbo Boost Technology 2.0.

With same code, one region is performing well, but other regions usually have CPU maxed out. On talking to Microsoft support, they said processors are assigned randomly and they cannot change it.

Only option suggested by support, that we try change the cluster and node by stopping and starting all VMSS instance at the same time in the Azure portal manually.

If we look at the performance benchmark for 2 processor assigned to us:

https://www.cpubenchmark.net/compare/Intel-Xeon-E5-2673-v4-vs-%5BDual-CPU%5D-Intel-Xeon-Platinum-8171M/2888vs3220.2

Now the only option we are left with is try restarting VMSS for n number of times or upgrade to different size.

Anyone faced similar situation? If yes what was the resolution?

Or any information, what are the design consideration by which Microsoft assigns a particular processor to the VM?

Answer 1

I wouldn't read too much into the comparative specs between each processor because you're ultimately not getting the full processor - you're only buying the vCPUs. Each is are supposed to have similar performance from one to another. This would suggest that Microsoft may pack more VMs onto an 8171M host than onto an E5-2673 so the vCPUs across either machine are closer in performance equivalency within the SKU series.

Put simply, you have no idea how many VMs Microsoft is running off any given processor and it would only make sense that they run more off a higher performing host system.

If you want to have full operational performance of the processor, you'd have to buy a dedicated host. Note that the pricing sheet names precisely which processor SKU you get for your money unlike the vCPU mix and match happening in the D#_v2 SKU series.