Troubleshooting "Cannot connect to storage" Alarms Due to Inconsistent LUN Presentation on ESXi 8.0

Products

• VMware vSphere ESXi

Issue/Introduction

This article explains how to identify and resolve "Cannot connect to storage" and "Path degradation" alarms triggered by storage array re-provisioning events. These alerts often occur when a LUN ID is reused for a new volume without unmounting the previous device, causing a UID mismatch in ESXi.

Symptoms:

• Critical "Cannot connect to storage" or "Path degradation" alarms in vCenter.
  
  
  
  
• vmkernel.log displays NMP: vmk_NmpVerifyPathUID errors indicating a UID change for a device path.
  
ALERT: NMP: vmk_NmpVerifyPathUID:####: UID of a device (path vmhba#:##:##:####) has changed from naa.################# to naa.#################. Critical error if data LUN.


• SCSI Sense code 0x6 0x29 0x0 observed in logs, indicating a device reset or storage condition change.
  
  VMW_SATP_ALUA: satp_alua_issueCommandOnPath:###: Path (vmhba#:##:##:####) command 0xa3 : Failed with transient error status Transient storage condition, suggest retry. sense data: 0x6 0x29 0x0.
vmkernel: cpu13:###### ScsiDevice: ####: Handle REPORTED LUNS CHANGED DATA unit attention
  
  
  
• ESXi logs indicate "Permanently inaccessible device" (PDL) for existing NAA-IDs.
  
  vmkwarning: cpu2:#####)WARNING: ScsiDevice: ####: Device :naa.#################  has been removed or is permanently inaccessible.

Environment

VMware vSphere ESXi 8.x

Cause

The issue is caused by a live LUN identity swap. When a storage array replaces a volume with a new shared volume but retains the same LUN ID, ESXi Native Multipathing (NMP) detects that the Unique Identifier (NAA-ID) on the active path no longer matches its cached record. To prevent data corruption from writing to the wrong physical volume, ESXi invokes PDL protection and severs the path.

Resolution

1. Clear Residual Alarms:

   1. In the vSphere Client, navigate to the affected ESXi host(s) and cluster.
   2. Select the triggered "Cannot connect to storage" alarms.
   3. Click Reset to Green (or Acknowledge) to clear the historical alerts.

2. Execute Cluster Storage Rescan:

   1. Right-click the target cluster in the vSphere Client.
   2. Navigate to Storage > Rescan Storage.
   3. Select both Scan for new Storage Devices and Scan for new VMFS Volumes.
   4. Click OK. This flushes stale APD/PDL mappings and synchronizes the active device table.

3. Verify Operational Paths:

   1. Navigate to Configure > Storage > Storage Devices on the hosts.
   2. Confirm that only the expected target volume (new NAA-ID) and its active paths are registered.

Additional Information

• For instructions on gathering diagnostic data, see Collecting diagnostic information for VMware ESXi.
• To speak with a customer representative or a Support Engineer see Contact Support. Scroll to the bottom of the page and click on your respective region.