Measure combined workload demand before choosing a constrained-vCPU Azure size

Source facts

Azure offers predefined constrained-vCPU sizes that expose fewer processors while retaining the base size’s memory, storage, and I/O bandwidth specifications. Disabled vCPUs are unavailable to the guest. Microsoft warns that a VM hosting several workloads may therefore need more active vCPUs than a single-workload assessment suggests. Microsoft Learn.

Applicability

Evaluate a specific offered size and its documented base-size relationship. Inventory the database and every accompanying service or scheduled task that will remain on the VM. Keep this technical sizing review separate from any commercial or licensing assessment; no financial outcome is assumed here.

DSE recommendation

Measure the database and its accompanying tasks together before accepting the lower active-vCPU count. Ask the workload owner to identify overlapping peaks, maintenance activity, and acceptable response-time limits. Compare a constrained option with its base size using the same representative test conditions. If a secondary task will be moved elsewhere, make that relocation an explicit prerequisite rather than silently excluding its demand from the calculation.

Verification

On the approved candidate VM, inspect the processor count exposed to the guest and reconcile the memory and I/O specifications with the selected size. Run the agreed mixed workload, including the relevant maintenance overlap, and retain application response times and processor observations. Reject the proposal if it meets the primary workload’s quiet-period needs but fails the combined acceptance criteria. Document the tested workload composition alongside the final size decision.

Official references

Microsoft Learn: Constrained vCPU sizes. Source reviewed September 9, 2026.