VMFS Datastore is showing zero size after performing failback on NetApp MetroCluster

Products

• VMware vSphere ESXi
• VMware vSphere ESX 8.x

Issue/Introduction

Symptoms:

• A VMFS datastore shows zero size in the vSphere Client (Datastores & Clusters Inventory Tab -> Choose Datastore):
  
  

• The LUN backing the datastore is located on a NetApp MetroCluster.
• You recently performed a failover and failback of the LUN's on the NetApp MetroCluster.
• The NetApp MetroCluster is using SnapMirror active sync (SM-as) for LUN replication.
• The vmkernel.log shows numerous errors similar to the following:

2025-11-11T20:00:00.000Z In(182) vmkernel: cpu3:XXXXXXX)NMP: nmp_ThrottleLogForDevice:3898: H:0x0 D:0x2 P:0x0 Valid sense data: 0x2 0x4 0xa Act:FAILOVER. cmdId.initiator-0xYYYYYYYYYYYY CmdSN 0xZZZZZZ

Environment

• VMware vSphere 8.x

Cause

• This is not a VMware issue.
• The above error: H:0x0 D:0x2 P:0x0 Valid sense data: 0x2 0x4 0xa indicates that the SAN is reporting that the LUN is in a "Not Ready" state.  The D:0x2 portion of the error indicates that the error was returned by the SAN itself.
• This is an issue with the Snap Mirror active sync being out of sync.

Resolution

• Please contact NetApp for verification and further troubleshooting and resolution of the out-of-sync state.

Additional Information

• For more information on interpreting SCSI Sense Codes, see KB: Interpreting SCSI sense codes in VMware ESXi
• For more information on NetApp MetroClusters, see Vendor documentation: MetroCluster Documentation
• For more information on Snap Mirror active sync, see Vendor documentation: Learn about ONTAP SnapMirror active sync