VMkernel log reports the error: Partition: 420: Missing prot MBR label for naa.xx

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms:

• In the /var/log/, you see the log spew:
  
  Partition: 420: Missing prot MBR label for "naa.xxx"
  
  
• The datastore is mounted and you are able to access the data within the datastore

Environment

VMware vSphere ESXi 5.0
VMware vSphere ESXi 5.1

Cause

This issue occurs when the GPT partition on the disk is valid, but the protective Master Boot Record (MBR) Extended Partition Pointer is missing.

Resolution

The GPT partition contains a backup of the partition table in the last sector of the disk. To resolve this issue, recover the primary partition table from the backup using the partedUtil utility.

To recover the primary partition table using partedUtil :

1. Open a console to the ESXi/ESX host. For more information, see Using Tech Support Mode in ESXi 4.1 and ESXi 5.x (1017910).
2. Verify if GPT partition is valid using this command:
   
   partedUtil getptbl /vmfs/devices/disks/DeviceName
   
   For more information, see Using the partedUtil command line utility on ESXi and ESX (1036609).
   
   
3. Back up the first 1.2 GB of the disk by running this command (saving the information under /tmp):
   
   dd if=/vmfs/devices/disks/DeviceName of=/tmp/naaXXX.dd bs=1M count=1200
   
   
4. Run this command to fix the partition:
   
   partedUtil fix /vmfs/devices/disks/DeviceName
   
   
5. Refresh the datastores using this command:
   
   vmkfstools -V

Additional Information

• This issue may also occur due to pre-existing or incompatible information on the hard disk that prevents the disk from being formatted. To resolve this issue, you must create a new label.
  
  To create a new label, run this command:
  
  # partedUtil mklabel /vmfs/devices/disks/DeviceName gpt
  
  Caution: This operation deletes all pre-existing partitions on the device. The changes take effect immediately. This results in data loss and cannot be reverted.
  
  
• If the GPT partition includes protective MBR, running the fdisk -l command on the device reports the error:
  
  Found valid GPT with protective MBR; using GPT

Using Tech Support Mode in ESXi 4.1, ESXi 5.x, and ESXi 6.x
Using the partedUtil command line utility on ESXi and ESX