windows
(Failover Cluster) Domain Controller의 역할
아이셩짱셩
2025. 5. 30. 11:35
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🧠 TL;DR Summary:
✅ A Domain Controller (DC) is required for:
- Cluster formation and authentication
- Name resolution (via DNS)
- Accessing domain-joined resources (e.g., SMB)
- Cluster-aware updates, GPOs, and live migration authentication
However, once the cluster is already formed, certain operations (like S2D and CSV access) can continue without the DC — but with reduced functionality and higher risk.
🔍 1. Domain Controller's Role in Failover Clustering
| Function | Role of Domain Controller |
| Cluster Creation | Required — nodes must authenticate with the domain to form/join the cluster. |
| Cluster Startup | Required — during initial boot, cluster service authenticates via the domain. |
| Quorum Witness Access (File Share) | Must resolve and authenticate to access file share quorum. |
| Cluster Name Object (CNO) | Stored in Active Directory. Requires DC to register and update. |
| Live Migration | Uses Kerberos authentication → requires DC & DNS. |
| DNS Resolution | All cluster nodes resolve cluster name, witness, and partners through DNS. |
| Hyper-V Authorization | Uses AD credentials for remote management, permissions, and constrained delegation. |
💡 Without a reachable DC, some features will hang or fail (especially Live Migration, witness arbitration, or remote cluster management).
📦 2. Domain Controller's Role in S2D and CSV
| Feature | Dependency on DC |
| Storage Spaces Direct (S2D) | ❌ No direct dependency once initialized. |
| Cluster Shared Volumes (CSV) | ❌ CSV redirection and IO can still function without AD. |
| Cluster Health Service | ✅ Requires AD for some telemetry/reporting features. |
| Cluster-Aware Updating (CAU) | ✅ Requires domain credentials & GPOs. |
✅ Good news: S2D & CSV can keep running for a time without AD, assuming cluster membership is intact.
❗ But if the cluster service restarts on a node, or if Live Migration or authentication is needed — the absence of a DC causes issues.
🚫 What Fails Without a DC
| Component | What Fails Without DC |
| Cluster Name Resolution | Cluster name (CNO) might not register; clients can't connect. |
| File Share Witness | Unreachable — quorum may be lost. |
| Live Migration | Kerberos fails — migration errors occur. |
| Cluster Join/Restart | Nodes can't rejoin cluster if DC is unreachable during boot. |
| Hyper-V Replica / SMB | May fail due to auth issues. |
| Remote Management | MMC, DMC, PowerShell remoting may fail (depends on delegation/auth). |
✅ Best Practices
- Always have at least 2 DCs — preferably one outside the cluster (e.g., physical, VM on another host, or cloud-hosted).
- Ensure DC/DNS is reachable via multiple cluster networks.
- Use cloud witness (Azure) or file share witness outside the cluster — don't place the witness on a clustered VM.
- Avoid putting all your DCs as VMs on the same S2D cluster — major SPOF risk.
🔄 Bonus: If Your DC is on the Same Cluster...
- Boot order becomes critical.
- Cluster might hang on start if:
- The DC VM isn't online.
- DNS isn't reachable.
- Kerberos fails.
👉 Workaround: Set one cluster node to delay booting cluster service until DC is up, or configure DC to start on all nodes (not ideal).
🧪 Want to Test It?
- Try simulating a DC outage and observe:
- Can nodes stay in the cluster?
- Can you migrate VMs?
- Can you connect from Failover Cluster Manager?
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