Mastering Windows Server 2016 Hyper-V

perform a backup at the Hyper-V host or even a checkpoint is not possible. Backups
would need to be taken within the guest virtual machine. Storage migration is also not
supported for shared VHDX files. This also means Hyper-V Replica cannot be used for
virtual machines that are connected to a shared VHDX file.

When using Shared VHDX on an SMB 3 share, an entirely new protocol called Remote
Shared Virtual Hard Disk Protocol is used. This protocol leverages SMB as a transport
but is not part of the SMB protocol itself.

Windows Server 2016 evolves shared VHDX to remove three key limitations of the
Windows Server 2012 R2 implementation and enables:

Dynamic resizing    of  a   shared  VHDX

Backup  of  shared  VHDX    at  the host    level

Replication of  a   shared  VHDX    using   Hyper-V Replica

Note that live storage move and checkpointing of shared VHDX files is not possible in
Windows Server 2016. To enable these new features of shared VHDX files, it has
transitioned to a new feature called VHD Sets. VHD Sets accomplishes the same result
as shared VHDX—the ability to share VHDX files between multiple hosts—but it is
implemented differently.

VHD Sets uses a new type of VHD file, which signifies that it is a VHD Set. The actual
VHDS file is only 260KB, and an automatically generated file (AVDHX) is created to
hold the content of the VHD Set. The view of the files on disk for a VHD Set are shown
in Figure 4.29. Notice the small VHDS file and the larger AVHDX containing the actual
data.

Figure 4.29 VHD Set files on disk

A VHD Set can be fixed or dynamic, which will impact the size and behavior of the
AVHDX file. To use VHD Sets, the process is different than in Windows Server 2012
R2:

1 . Create  a   new VHD Set file.   If  using   Hyper-V Manager,    choose  New ➢   Hard    Disk

from    the host    actions menu,   and for the format  select  VHD Set,    as  shown   in  Figure

4.30.   The remaining   options are the same    as  for a   regular VHDX    file    creation.   If

using   PowerShell, specify an  extension   type    of  vhds    with    the New-VHD cmdlet. This

should  be  created on  a   Cluster Shared  Volume, which   is  still   a   requirement for

VHD Sets.

2 . Attach  the VHD Set to  multiple    VMs by  selecting   the option  to  add a   Shared  Drive

to  the SCSI    Controller  and then    selecting   a   VHDS    file,   as  shown   in  Figure  4.31.   If

using   PowerShell  with    the Add-VMHardDiskDrive cmdlet, use the -

SupportPersistentReservations   parameter   and specify the vhds    file.