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Case Study: London Borough Barnet: Migration of 133 Critical Workloads from Legacy Nutanix to Microsoft Azure

Customer Problem – What They Were Hoping to Change

The London Borough of Barnet, one of the largest boroughs in London (population ~400,000), was operating its core IT infrastructure across two third-party hosted data centres (Cody Park and Spring Park), running a mix of traditional VMware and Nutanix hyper-converged systems. Much of the environment fell under the long-standing Capita outsourcing partnership (CSG contract), with ageing hardware nearing end-of-support, escalating co-lo/hosting costs, and limited agility to support modern citizen services.

Key pain points at the start of the project:

  • Exit expensive third-party data centre contracts and reduce fixed IT costs amid severe local government budget pressures
  • End reliance on the Capita CSG partnership (set to fully conclude by 2026, with IT services extended only for orderly transition)
  • Achieve greater control, resilience, and scalability for critical civic applications (revenues & benefits, housing, planning, social care, Mosaic adult social care system, customer portals, and geographic information systems)
  • Deliver zero-downtime migration in a highly regulated PSN-protected environment while maintaining ISO 27001 and PCI-DSS compliance

The customer wanted to exit both legacy data centres completely, eliminate on-premises infrastructure, and move to a fully managed cloud platform that would reduce costs, increase agility, and provide enterprise-grade resilience.

 

The Challenge

Decommission two physical data centres hosting 133 production virtual machines (with ±10% variation) while maintaining zero downtime for business-critical applications (collections and, customer portals). The environment included a mix of Windows and Linux workloads, SQL Server databases, and strict regulatory requirements.

Our Solution – How We Helped Solve the Problem

We delivered a structured, low-risk “lift-and-shift” (rehost) migration to Microsoft Azure using Azure Migrate and Azure Site Recovery, executed in controlled 2-week sprint waves. Each wave lasted up to 6 weeks (discovery → design → test migration → cutover → validation).

Microsoft technologies used:

  • Azure Migrate (discovery, assessment, dependency mapping)
  • Azure Site Recovery (replication and orchestrated failover)
  • Azure VM (Iaas – Windows and Linux)
  • Azure Virtual Network and VPN Gateway (hybrid connectivity during migration)
  • Azure Private Link and Private Endpoints (secure connectivity for on-prem tools)
  • Azure Backup and Azure Site Recovery (disaster recovery post-migration)
  • Azure Monitor and Log Analytics Workspace (centralised monitoring)
  • Azure Policy and Blueprints (governance and tagging enforcement)
  • Azure Cost Management + FinOps practices

How the team solved the problem:

  • Project Initiation and Discovery: Full application passporting and dependency mapping using Azure Migrate.
  • Wave and Sprint Planning: Applications grouped into 8 migration waves by business criticality and dependencies. Priority agreed jointly with the customer and business stakeholders.
  • Pre-migrations: Detailed solution design documents produced and signed off. All required Azure resources (VNet, NSG, subnets, bastion, etc.) deployed via Infrastructure-as-Code.
  • Replication and Testing: Non-production test migrations performed first, followed by production replication using Azure Site Recovery.
  • Cutover Windows: Weekend cutovers with final delta sync and DNS/update of load-balancer records.
  • Post-migration Optimisation: Right-sizing recommendations applied, Azure Hybrid Benefit leveraged for Windows/SQL licensing.
  • Decommission: Powered down and physically removed Nutanix clusters at both Cody Park and Spring Park once final sign-off achieved.

Results 

By moving from a co-location and Capita-managed infrastructure to Microsoft Azure, the organisation achieved significant operational and financial improvements. Annual data centre and hardware-related costs, previously between £350,000 and £500,000, were completely eliminated as both physical facilities were decommissioned. Over a three-year period, total infrastructure TCO dropped from £1.5–£1.9 million to £950,000–£1.25 million, thanks to optimised Azure consumption—representing a 30–40% reduction.


Provisioning speed improved dramatically, with new virtual machines now deployed in under 10 minutes compared to the previous 4–8 week timeframe, delivering over 99% faster turnaround. Business continuity also strengthened, as Recovery Point Objective (RPO) and Recovery Time Objective (RTO) for critical civic systems improved from 8–24 hours and 24–72+ hours respectively to less than 15 minutes and under 2 hours, enabled by geo-redundant Azure Site Recovery—a 95%+ improvement.


Maintenance disruptions were virtually eliminated, reducing downtime from 12–20 weekends per year to near zero. The organisation also achieved a complete exit from physical data centres, consolidating operations entirely in the cloud. Finally, all 133 workloads were successfully migrated within ±10% tolerance, with zero downtime, ensuring a seamless transition.

Additional soft benefits:

  • IT team freed from hardware break-fix and capacity planning
  • Built-in geo-redundant disaster recovery across UK South and UK West
  • Foundation laid for future modernisation (Azure App Service, AKS, etc.)

Why This Story Is Interesting 

“LB Barnet Council exits two legacy data centres completely, saves over £400k in three years, and achieves true cloud agility by migrating 141 critical workloads to Azure with zero downtime.”

This project stands out as a textbook example of a successful large-scale regulated-sector data centre exit in under 10 months, delivering both immediate cost savings and a future-proof platform using only native Microsoft Azure migration tools.

Lessons Learned

  • Collaboration and transparency are critical for long-term cloud success.
  • Hybrid expertise (on-prem and cloud) ensures smooth transition.
  • Backup and remediation planning are essential for risk mitigation.

“Trustmarque have consistently worked closely with the team, developing a tight day to day working relationship. Again and again the Trustmarque team have gone above and beyond”

IT Director

 

Expand your capabilities with Azure Managed Services

In March 2023, out of 400,000 global organisations in the Microsoft Partner Network, Trustmarque received the sixth designation in ‘business applications’. By succeeding in all six designations, we unlocked the highest tier of the program and receive the seventh designation for overall excellence in the Microsoft Cloud.

Building on this, our Managed Services build on our partner-led approach, giving you access to technical expertise, innovative solutions and best practice approaches that bring real benefits, not least cost optimisation.

If you’re planning your migration to Microsoft Azure or already on that journey, contact us for a consultation to see how we can help.

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