Fix QUORUM_RESOURCE_ONLINE_FAILED (0X000013A3) – Quorum won't start

Quick Answer

Open Disk Management (diskmgmt.msc), find the quorum disk (usually labeled as a witness or quorum), right-click it and select Online. Then go to Failover Cluster Manager > right-click the cluster > More Actions > Configure Cluster Quorum Settings to reassign the witness.

Why This Happens

This error shows up when the quorum resource (the disk that decides which node keeps the cluster alive) won't start. It's common after a server reboot, a disk failure, or a storage connectivity issue. I've seen it most often on Windows Server 2016 and 2019 clusters where the witness disk went offline due to a lost SAN path or a stale disk signature. The cluster can't form without quorum, so the whole cluster goes down.

The real trigger? Someone rebooted a node, and the shared disk didn't come back online fast enough — or the disk got corrupted when the node crashed. The cluster then can't agree on which node holds the valid copy, so it throws this error.

Step-by-Step Fix

1. Open Disk Management. Press Win + R, type diskmgmt.msc, hit Enter. Wait for the list of disks to load. Expect to see all disks listed; the quorum disk will show as Offline (if it's red and has a down arrow).
2. Bring the quorum disk online. Right-click the disk that's Offline — it's usually the one labeled as a witness or quorum in the Cluster Manager. Select Online. The disk status should change to Healthy (Online).
3. Open Failover Cluster Manager. Type cluadmin.msc in Run. Click OK. You'll see your cluster name, possibly with a red X or warning.
4. Check the quorum configuration. Right-click the cluster name (top of the tree) and go to More Actions > Configure Cluster Quorum Settings. Click Next. Choose Select the quorum witness, then pick Configure a disk witness. Find the disk you just brought online and select it. Click Next, then Finish. The cluster should now show the quorum resource as Online.
5. Validate the cluster. Right-click the cluster again and go to Validate Cluster. Run all tests. This confirms the disk is working and the cluster is healthy. If tests pass, the error is gone.

Alternative Fixes

If the disk won't come online in Disk Management (greyed out or shows errors):

• Check the SAN or iSCSI connection. Open iSCSI Initiator or Storage Manager. Make sure the disk is visible and the connection is active. Rescan for disks in Disk Management after fixing the connection.
• Use the command line to force the disk online. Open PowerShell as Administrator. Run Get-Disk | Where-Object {$_.OperationalStatus -eq "Offline"} to find the disk number. Then run Set-Disk -Number X -IsOffline $false (replace X with the disk number). The disk should come online immediately.
• Try a different witness. If the disk is corrupted and can't be fixed, go to Configure Cluster Quorum Settings and choose a file share witness instead of a disk witness. This works fine for clusters that don't have a dedicated shared disk.
• Rebuild the quorum disk. If the disk is dead, you'll need to create a new quorum disk in the SAN or use a different LUN. Then reassign it in the cluster settings.

Prevention Tip

Set the quorum disk to auto-online in Disk Management. Right-click the disk, go to Properties > Policies, and check Enable automatic online of the disk. This prevents it from staying offline after a reboot. Also, make sure the disk has a unique, static MPIO path — I've seen lost paths cause this error more than anything else.

Pro tip: Keep a spare witness disk LUN in your SAN. If the primary fails, you can reassign the cluster quorum in under a minute instead of waiting for storage support.