An unresolved VMFS volume with signature xxxxxxxx-xxxxxxxx-xxxx-xxxxxxxxxxxx has been detected on this disk.
Article ID: 399295
Updated On:
Products
Issue/Introduction
When adding that has been presented from Netapp as a snapmirror lun. Three options are provided to the customer.
Environment
ESXi 7.X and above
Resolution
When you're mounting a VMFS volume on a LUN and see the option:
Assign a new signature
Data on the disk will be retained. A new signature will be assigned to the datastore and references to existing signature from VM configuration files will be updated. Datastore will be mounted using the original name.
Keep existing signature
Data on the disk will be retained. The datastore will be mounted using the same signature. Datastore will be mounted using the original name.
Format the disk
The current disk layout will be destroyed and all data will be lost permanently.
This is an important decision point in vSphere. Here's what it means and when to use it.
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What does "Keep Existing Signature" mean?
Every VMFS datastore has a unique signature (UUID). When ESXi detects a LUN that already contains a VMFS signature, it offers three choices:
1. Keep Existing Signature ( SAFE)
Mounts the LUN using its current VMFS signature without changing anything.
Use this if:
- You're reconnecting a previously used datastore.
- You're restoring access after a reboot or rescan.
- The volume is shared between hosts (e.g., in a cluster).
This will mount the datastore exactly as it was, with the **same name**, **UUID**, and **VMs** intact.
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2. Assign a New Signature ( Clones or snapshots)
Creates a new UUID and datastore name, treating it like a new datastore.
- Use this if the LUN is a clone or snapshot of a live VMFS datastore.
- Prevents conflicts from two datastores with the same UUID on different hosts.
Typically results in a name like `snap-datastore_name`.
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3. Format the Disk ( Destroys data )
Erases the existing VMFS volume and creates a new empty datastore.
Only use if you're **100% sure** the disk is no longer needed.
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When to Choose "Keep Existing Signature"
| Scenario | Choose "Keep Existing Signature"? || ------------------------------------- | --------------------------------- || Reconnecting a known datastore | ✅ Yes || Re-attaching storage after failover | ✅ Yes || Restoring LUN access after rescanning | ✅ Yes || Connecting a clone of another LUN | ❌ No – Use “Assign New Signature” || Disk will be used as RDM | ❌ No – Don't mount it as VMFS |
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Tip:
Always verify the LUN contains the correct data before mounting.
You can use the VMFS UUID or datastore name to confirm it's the right volume.
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