HCX Migrations and VM Disk UUIDs

What are you talking about Gabe? WHAT ARE VM UUIDS?

Universally Unique Identifiers are generated for each virtual machine disk when a VM is created. You can see the identifiers by running the vmkfstools on the on the ESXi host:

What happens to the virtual disk UUIDs during HCX Migrations?

  • HCX vMotion
    With HCX vMotion, the disk UUIDs are not changed. vMotion uses the source site vm config spec; there is a vim.vm.device.VirtualDisk configuration that references the original disk UUID.
  • HCX Bulk Migration and Replication Assisted vMotion (RAV)

    With HCX Bulk Migration, the disk UUIDs will change. The APIs used for creating the virtual machines from the VMX config file, during a Host Based Replication operation, do not have the capability of retaining the disk backing UUIDs.

    With RAV migrations, the disk UUIDs will change. During the migration switchover, when HCX vMotion is engaged for delta vMotion, the replicated virtual machine will have already been created with new disk UUIDs using the same approach as with HCX Bulk migration.

Why does this matter?

There are multi-disk virtual machines with OS level storage management elements out there. Those may contain disk UUID references. Changes to the disk UUIDs in this case can be disruptive to those storage management functions.

It is recommended to use the HCX vMotion when the applications have disk UUID related dependencies.

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