Introduction

High availability (HA) is critical for modern organizations that cannot afford downtime of shared resources such as file shares, departmental data, and application-level files. Windows Server 2025 introduces performance improvements, enhanced cluster resiliency, and better storage integration—making it an excellent platform for building a highly available File Server Failover Cluster.

In this guide, you will learn exactly how to set up a Windows Server 2025 failover cluster for file server high availability using shared storage—ideal for enterprises, SMBs, and IT labs.

What You Need (Prerequisites)

Before you begin, ensure the following:

1. Hardware / Virtual Machines

You need at least two cluster nodes:

• Node1 – Windows Server 2025 (Datacenter recommended)
• Node2 – Windows Server 2025
• Shared Storage via:
  • iSCSI Target Server
  • SAN Storage
  • Storage Spaces Direct (S2D)
  • Fibre Channel storage

Important: Each node must access the same shared LUN(s) with persistent reservation support.

2. Network Requirements

Recommended network design:

Network Best Practices

• Enable Jumbo Frames for iSCSI traffic.
• Keep storage traffic isolated (VLAN or separate switch).
• Enable NIC Teaming on management adapters (optional).

3. Active Directory Requirements

• All nodes must be joined to the same AD domain.
• You need a domain account with Domain Admin + Local Admin permissions.

4. Shared Storage Requirements

You need at least one shared disk:

• 1 x Quorum Witness Disk (optional if using Cloud Witness / File Share Witness)
• 1 or more x Data Disk(s) for File Server

5. Install Failover Clustering Feature on Each Node

Open PowerShell as Administrator:

Install-WindowsFeature -Name Failover-Clustering -IncludeManagementTools

Reboot the servers after installation.

Step-By-Step: Setup Failover Cluster for File Server HA

Step 1 — Validate Configuration

Windows Server 2025 requires cluster validation before creating the cluster.

Run the following on Node1:

1. Open Failover Cluster Manager
2. Click Validate Configuration
3. Add both servers:
   • NODE1.domain.local
   • NODE2.domain.local
4. Choose Run all tests
5. Complete the validation wizard.

If all tests pass → continue.
If warnings appear → review and fix (most warnings can be ignored, errors cannot).

Step 2 — Create the Failover Cluster

From Node1:

1. Open Failover Cluster Manager.
2. Click Create Cluster.
3. Add both nodes.
4. Specify the Cluster Name:
   • Example: FS-CLUSTER
5. Assign a Cluster IP Address:
   • Example: 10.0.10.50
6. Finish the wizard.

Cluster will now form and come online.

Step 3 — Configure Quorum (Highly Recommended)

Go to:
Failover Cluster Manager → Cluster Name → More Actions → Configure Cluster Quorum

Recommended Quorum Options:

• Cloud Witness (Azure Storage) → best for DR
• File Share Witness → for on-prem clusters
• Disk Witness → traditional method

For typical file server clusters, select File Share Witness.

Example PowerShell:

Set-ClusterQuorum -FileShareWitness \\DC01\QuorumWitness

Step 4 — Add Shared Storage to Cluster

1. Go to Storage → Disks in Failover Cluster Manager.
2. Click Add Disk.
3. Select the shared LUN(s).
4. Assign:
   • Disk1 → Cluster Shared Volume / Data
   • Disk2 → Witness (if you choose Disk Witness)

Convert Disk to Cluster Shared Volume (CSV)

Right-click the disk → Add to Cluster Shared Volumes

CSV paths look like:

C:\ClusterStorage\Volume1

Step 5 — Create a High Availability File Server Role

Now we configure the File Server as a cluster role.

1. In Failover Cluster Manager:
   • Right-click Roles → Configure Role
2. Select File Server
3. Choose File Server for General Use
   • (If you host SMB shares, select this)
4. Provide the File Server Name:
   • Example: FS-SHARE01
5. Assign a unique IP address:
   • Example: 10.0.10.60
6. Select the storage disk (CSV)
7. Finish the wizard.

The File Server role is now online.

Step 6 — Create Highly Available File Shares

Now create shares that automatically move between nodes during failover.

To create a share:

1. Go to Roles → FS-SHARE01
2. Right-click → Add File Share
3. Choose:
   • SMB Share / Quick
   • SMB Share / Advanced (recommended for production)
   • SMB Share with Continuous Availability (for application workloads)
4. Select CSV volume
5. Enter share name:
   • Example: DepartmentData
6. Configure permissions:
   • Department groups
   • Administrators
   • Backup Operators
7. Enable:
   • Continuous Availability (if required)
   • Access-based enumeration

Finish the wizard.

Step 7 — Test Failover

To test high availability:

1. In Failover Cluster Manager
2. Select Roles
3. Right-click the file server role (FS-SHARE01)
4. Click Move → Select Node
5. Choose Node2

Observe:

• Clients still access the share without interruption
• File Server role comes online on Node2
• No data loss

Failover Testing Using PowerShell

Move-ClusterGroup -Name "FS-SHARE01" -Node NODE2

Monitoring the Cluster (Windows Server 2025)

Server 2025 provides enhanced monitoring:

Use the new Cluster Dashboard:

• Node health
• Storage I/O
• Failover events
• Witness status
• CSV performance metrics

You can open it from:

Server Manager → Tools → Failover Cluster Manager → Dashboard

Conclusion

Setting up a File Server Failover Cluster on Windows Server 2025 gives your organization true enterprise-grade high availability. With shared storage, properly configured networks, and cluster roles, your file services remain accessible even if one server goes offline.

This architecture ensures:

• Zero downtime during patching
• Seamless failover between nodes
• Better resiliency and improved user experience