Right-sizing VMs after migration

Overview

Lift-and-shift VMs often arrive oversized because on-prem was padded for hardware renewal cycles. Post-migration rightsizing protects margin and client satisfaction.

Data collection

30–60 days of CPU, memory, disk IOPS, and network from Azure Monitor, CloudWatch Agent, or guest perf counters—not just hypervisor averages.

Process

1. Exclude known peak season windows unless client agrees.
2. Compare p95/p99 utilization to SKU headroom; prefer the next smaller family with equivalent disk performance.
3. Test memory pressure on Linux with available not just free; on Windows use committed bytes vs limit.
4. Change size in maintenance window; watch application licence constraints (BYOL, vCPU minimums).

Governance

Tag rightsizing candidates in a spreadsheet linked to the PSA project; get written approval for production changes. Document “we recommended X; client deferred” for renewals.