Local Datastore missing after BOOTLUN migration

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms:

• There is a requirement to migrate the BOOTLUN from one storage model to another (e.g., Hitachi to Pure).

• The LUN size configured as BOOTLUN is less than 32GB.

• The BOOTLUN was originally configured on ESXi 6.7 and later the hosts were upgraded to ESXi 7.0. 

• During the BOOTLUN migration, the LUNs are not cloned at the storage level. Instead, LUNs from the new storage array are presented and the ESXi hosts are reinstalled.

• After reinstalling the ESXi hosts, the local datastore previously present on the BOOTLUN is missing.

Validation Steps:

• Run the following command to check the partition details of the BOOTLUN: partedUtil getptbl /vmfs/devices/disks/naa.xxxxxxxxxxxxxxxxxxxx
  
  Observe the output:
   • There is no VMFS partition present.
   • The entire LUN capacity is allocated to the vmfsl partition.
   
  Sample output:

  partedUtil getptbl /vmfs/devices/disks/naa.624axxxxxxxxxxxxxxxxxxxxxxxxxx
gpt
4177 255 63 41943040
1 64 204863 C12A7328F81F11D2BA4B00A0C93EC93B systemPartition 128
5 208896 8595455 EBD0A0A2B9E5443387C068B6B72699C7 linuxNative 0
6 8597504 16984063 EBD0A0A2B9E5443387C068B6B72699C7 linuxNative 0
7 16986112 41943040 4EB2EA3978554790A79EFAE495E21F8D vmfsl 0

• On the vSphere client, this device shows as Not Consumed under Hosts>Configure>Storage Devices

• It is listed when attempting to create a new datastore. However, no free space is available to create the vmfs partition.
  
  

Environment

VMware vSphere ESXi 7.x

Cause

With the introduction of ESXi 7.0, a new system-storage boot media layout was implemented. This layout can consume up to 138GB of disk space, leaving insufficient free space for a VMFS datastore on smaller boot LUNs.

• If the boot media is less than 142GB, there is not enough space to automatically create a VMFS datastore.
• A VMFS datastore (minimum size 4GB) is only created if the boot media is 142GB or larger.
• In cases where the boot LUN is less than 32GB, the entire disk is utilized for system partitions, preventing datastore creation.

Resolution

This is an expected behaviour if the size of the BOOTLUN is less than 142GB. You can consider the following options:

1. Use a larger BOOTLUN
   Ensure the BOOTLUN size is at least 142GB to allow ESXi to automatically create a VMFS datastore.
   
   
2. Manually Create a Datastore on a Separate LUN
   If increasing the BOOTLUN size is not an option, provision a separate LUN for VM storage.

Additional Information

ESXi System Storage Changes