Migrating RDM Backing Files for Clustered VMs

Products

• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

This article provides steps to move the underlying backing files of an MSCS virtual machine between datastores.

For more information, see Guidelines for Microsoft Clustering on vSphere.

 

Note: This article is intended for RDM based clusters and not shared VMDK clusters.

 

Symptoms:

• Unable to perform VMware vMotion or VMware Storage vMotion on Microsoft Cluster (MSCS) virtual machines that use a shared disk configuration.
• Virtual machines with SCSI bus sharing enabled cannot be vMotioned or Storage vMotioned while powered on.
• A cold migration of a virtual machine with Raw Device Mapping (RDM) results in the RDM being copied to a new VMDK file.

Environment

VMware vCenter Server 8.0.x
VMware vCenter Server 7.x

VMware vCenter Server 6.x

VMware vSphere ESXi 8.0
VMware vSphere ESXi 7.x
VMware vSphere ESXi 6.x

Cause

• RDM disks maintain SCSI-3 persistent reservations for cluster coordination
• Storage operations can disrupt these reservations
• Disk device reconnection during vMotion can trigger cluster protective measures

Resolution

Caution: Before performing the proceeding steps, take a full backup of all virtual machines and document RDM mappings details.

 

Note: VMware recommends to performing these steps in a maintenance window as Cluster VMs will be powerOff.

 

• To move the underlying backing files of an Clustered virtual machine between datastores:

1. 1. Shutdown the virtual machine 1.
   2. Remove (but do not delete) the RDM pointers from virtual machine 1.
   3. Cold migrate virtual machine 1 to the destination datastore.
   4. Shutdown the virtual machine 2.
   5. Create new RDM pointers on virtual machine 1.
   6. Power on virtual machine 1.
   7. Verify operating system and application functionality of virtual machine 1.
   8. Remove and delete the RDM pointers from virtual machine 2.
   9. Cold migrate virtual machine 2 to the destination datastore.
   10. Add existing RDM pointers (created in step 5) to virtual machine 2.
   11. Power on virtual machine 2.
   12. Verify cluster functionality.
   13. End maintenance window.

Additional Information

• vMotion and Storage vMotion are not supported on Microsoft Cluster (MSCS) virtual machines with a shared disk configuration.

For more information about recreating RDM mappings, see:

• • Migrating virtual machines with Raw Device Mappings (RDMs)
  • Guidelines for Microsoft Clustering on vSphere