All Datastores are Missing After Migrating SAN-backed Datastores to a New SAN

Products

• VMware vSphere ESXi
• VMware vSphere ESX 8.x
• VMware vSphere ESX 7.x
• VMware vSphere ESXi 8.0

Issue/Introduction

Symptoms:

• As part of a migration to a new SAN, the LUNs used for the datastore backing were replicated to new LUN's on a new SAN and subsequently mapped to the ESXi host(s).
• The old LUN's have now been unmapped from the ESXi host(s). 
• All of the VMs on the original datastores are now showing as invalid in vSphere Client.

Environment

• VMware vSphere ESXi (All Versions)

Cause

• The LUN(s) are detected as snapshot LUNs, so they are not automatically mounted to the host(s).
• The LUN's are detected as snapshots when the ESXi host does not confirm the identity of the LUN with what it expects to see in the VMFS metadata.
  
  

Verification:

• You can see that the LUN's are detected as snapshot LUN's when running the following command from ssh session:
  
  esxcli vmfs snapshot list


########-########-####-############
   Volume Name: MY_REPLICATED_DATASTORE
   VMFS UUID: ########-########-####-############
   Can mount: true
   Reason for un-mountability:
   Can resignature: true
   Reason for non-resignaturability:
   Unresolved Extent Count: 1

 

Resolution

• The datastore(s) will need to be resignatured and the VM's re-registered from the new datastores:
  
  
  • Follow the steps to resignature the datastore(s) in the following KB: Troubleshooting LUNs detected as snapshot LUNs in vSphere.
  • Once the datastore(s) are resignatured, all VM's referencing the old datastore(s) will have to be unregistered the hosts, then re-registered from the new datastores.
    • To unregister a VM, see TechDocs: Remove VMs or VM Templates from vCenter Server or from the Datastore.
      • NOTE: In this case, you only want to "Remove from Inventory".  DO NOT DELETE the VMs.
    • To re-register a VM, see TechDocs: Register a VM or VM Template with vCenter Server.