Cutting a US state agency's Windows Server licensing bill by 70% with mixed tenancy on AWS
The challenge
Public sector estates accumulate licensing. This agency held 2,146 cores of Windows Server Standard and 320 cores of Windows Server Datacenter, all purchased before October 2019 and therefore eligible for mobility to EC2 Dedicated Hosts. It also held 68 cores of SQL Server Enterprise and 206 cores of SQL Server Standard, all with active Software Assurance.
None of that entitlement appeared in a default licence-included migration model. Left unexamined, the agency would have paid AWS to licence software it had already bought, on an estate where Windows Server licensing alone ran to $296,579 a year and SQL Server licensing to $207,612.
The estate had a second problem. Discovery returned conflicting power states between the infrastructure snapshot and the utilisation collector, and a set of SQL servers was already under review for decommissioning. Migrating servers destined for shutdown inflates every downstream figure in the business case.
Our approach
We started with scope, not architecture. Fourteen servers flagged for decommissioning or shutdown review were removed from scope after reconciling the power-state discrepancy across both inventory sources. Two SQL Server Enterprise instances with no technical dependency on Enterprise features were re-priced as Standard, since the feature drivers most commonly cited, Transparent Data Encryption and Always On Availability Groups, both have alternatives available in Standard Edition or natively on AWS.
We then right-sized the surviving estate against measured utilisation rather than provisioned specification.
We modelled four commercial positions so the agency could see what each decision was worth:
- Direct match with no right-sizing, full licence included, as the lift-and-shift baseline
- Right-sized shared tenancy, full licence included
- Right-sized shared tenancy with SQL Server BYOL
- Mixed tenancy: 194 instances packed onto six EC2 Dedicated Hosts under Windows Server and SQL Server BYOL, with the remaining 278 instances on shared tenancy
The results
Windows Server licensing fell from $296,579 to $90,263 a year, a 70% reduction, using 304 Datacenter cores and 624 Standard cores the agency already owned.
SQL Server licensing fell to $0, covered by 30 Enterprise and 154 Standard cores against an entitlement of 68 and 206 respectively.
The recommended mixed-tenancy position sits 51% below the committed direct-match figure and 64% below direct match on demand.
Right-sizing, CPU optimisation and SQL Server consolidation also reduced the forward database requirement from 84 Enterprise cores to 30 and from 158 Standard cores to 108. That releases 38 Enterprise and 52 Standard cores against future true-ups and Software Assurance renewals, a saving that continues after the migration completes.
Why it matters
The single largest saving in this engagement came from paperwork rather than architecture. Reading the licence statement properly and mapping owned entitlement onto the right tenancy model was worth $206,316 a year on Windows Server alone, before any compute optimisation was applied.
Agencies with long procurement histories almost always own more than they think. The constraint worth knowing is that mobility to Dedicated Hosts requires licences purchased before October 2019, and version-locks the estate at Windows Server 2019. Both are checkable in an afternoon, and both change the answer.
Collection for this engagement ran through AWS Migration Evaluator. What that tool can and cannot see, including the four failure modes we check for every time: read the tool page →
Talk to us about your migration business case.
An OLA reconciles your Microsoft licence statement against measured utilisation and prices every tenancy model side by side, so the commercial decision is made on evidence rather than assumption.