After a power outage, the datastore fails to mount, displaying the error: "Unable to read head extent."

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms

• After a power outage, the datastore is missing from the vCenter and host inventory. 

Host inventory view

Issue Validation

• The device where the datastore was previously mounted is still visible under Host > Configure > Storage Devices in the vSphere Client.

• Running the partedUtil command confirms that the VMFS partition exists.

  partedUtil getptbl /vmfs/devices/disks/naa.600xxxxxxxxxxxxxxxxxxxxxxxxxxxx

  gpt

  2539818 255 63 40802189312

  1 2048 40802189276 AA31E02A400F11DB9590000C2911D1B8 vmfs 0


•  Attempting to mount the volume fails with the error: “Unable to read head extent.”

Environment

VMware ESXi 7.x 
VMware ESXi 8.x 

Cause

A misalignment in the data offset, causing a discrepancy between the actual size and the stored size within the LVM metadata. This happens when LVM metadata gets overwritten or corrupted. 

Cause Validation: 

• Reviewing the /var/log/vmkernel.log file on the ESXi host reveals events indicating a disk block size mismatch.

  2025-02-16T00:39:16.290Z cpu8:2102196) WARNING: LVM: 4302 [naa.600d0231000cb9cb567b448961376325:1: Disk block size mismatch (actual 512 bytes, stored 0 bytes, Physical Block Size 512 bytes)
2025-02-16T00:39:16.290Z cpu8:2102196) LVM: 4346: [naa.600d0231000cb9cb567b448961376325:1] Device expanded (actual size 40802187231 blocks, stored size 0 blocks)
2025-02-16T00:39:16.290Z cpu8:2102196) WARNING: LVM: 4393: [naa.600d0231000cb9cb567b448961376325:1] Misaligned data offset 0
2025-02-16T00:39:16.292Z cpu8:2102196) WARNING: LVM: 4302: [naa.600d0231000cb9cb5670cd806ea539d4:1] Disk block size mismatch (actual 512 bytes, stored 0 bytes, Physical Block Size 512 bytes)
2025-02-16T00:39:16.292Z cpu8: 2102196) LVM: 4346: [naa. 600d0231000cb9cb5670cd806ea539d4:1] Device expanded (actual size 12884897793 blocks, stored size 0 blocks)
2025-02-16T00:39:16.292Z cpu8:2102196) WARNING: LVM: 4393: [naa.600d0231000cb9cb5670cd806ea539d4: 1] Misaligned data offset 0
2025-02-16T00:39:16.299Z cpu62:2102201) NFS: 1333: Invalid volume UUID naa. 600d0231000cb9cb5670cd806ea539d4:1
2025-02-16T00:39:16.299Z cpu21:2102199) NFS: 1333: Invalid volume UUID naa. 600d0231000cb9cb567b448961376325:1

Resolution

Mounting the volume is not possible due to the corruption and overwriting of the LVM metadata. Restoring the data from a reliable backup is necessary to resolve the issue. 

Note: For further assistance, contacting Broadcom Support is advised.