Preserving host-level SQL Server licensing on AWS for a US county government

The challenge

The county ran three distinct on-premises environments: a geospatial platform, a physical security and video management platform, and a large SQL Server estate. The first two were straightforward. The third was not.

That SQL environment carried 117 in-scope Windows instances and 111 SQL Server Enterprise instances on a heavily oversubscribed VMware estate. The county had always licensed SQL Server at the host level. Software Assurance covered the physical cores of the underlying ESXi hosts, and VM density was absorbed by that host-level entitlement. Their position was 180 cores of SQL Server Enterprise with active Software Assurance, and that had comfortably covered the estate for years.

Moving to standard EC2 shared tenancy breaks that model completely. On shared tenancy, SQL Server BYOL is enforced at the individual virtual machine level, and every SQL VM carries its own four-core minimum regardless of how densely it was packed on-premises. Applied across 111 SQL Server Enterprise instances, the licensing requirement inflates far beyond the 180 cores already owned. Modelled as fully licence-included through Amazon RDS, the same database estate priced at $3.46M a year.

A conventional migration assessment would have returned that figure and stopped. The county would have concluded that migration was commercially impossible.

Our approach

We treated the county's licensing history as a design constraint rather than an inconvenience, and modelled the two AWS deployment options that preserve a host-level BYOL position for SQL Server.

EC2 Dedicated Hosts. Five R5 hosts on a four-active-plus-one-passive topology, at 48 physical cores each. SQL Server is licensed against the host's physical core count irrespective of how many VMs sit on it, mirroring the on-premises model exactly. That puts the requirement at 192 cores across the active hosts, with the passive host waived under the Software Assurance passive-failover benefit. Gap against current entitlement: 12 cores.

Amazon Elastic VMware Service (EVS). Five i4i.metal bare-metal hosts on the same 4+1 topology, at 64 physical cores each, running a managed VMware Cloud Foundation stack inside the county's own VPC. The full vSphere, vSAN and NSX stack is preserved, so virtual machines migrate as-is through HCX and vMotion with no re-platforming and no instance-by-instance right-sizing as a prerequisite. Each host ships with 30 TB of local NVMe, which absorbs the environment's allocated storage and removes the Amazon EBS line entirely. Gap against current entitlement: 76 cores.

We also priced a five-active EVS configuration with no HA spare. It raises the licensing requirement to 320 cores and a 140-core gap, so we modelled it and advised against it.

Both options were modelled on peak utilisation at 60% CPU and 80% RAM, in the us-east-1 region.

The results

Under both host-level options, SQL Server licensing appears as $0 on the AWS bill. It sits customer-side through Microsoft License Mobility with active Software Assurance.

EC2 Dedicated Hosts priced lower and closed the entitlement gap at 12 cores rather than 76. Amazon EVS priced higher but removed the storage line, retained the existing VMware operating model, automation and oversubscription patterns, and gave the lowest-friction migration path for a database estate the team did not want to re-platform. The county's operational continuity requirement carried the decision.

The consolidated recommendation placed the geospatial and video environments on shared tenancy and the SQL environment on Amazon EVS:

Why it matters

Working the estate through host-level deployment options held the SQL environment at roughly 16% of the licence-included figure, an 84% reduction, and converted an open-ended commercial risk into a defined 76-core procurement the county could budget for before migration began. That is the difference between a migration business case that stalls and one that proceeds.