VSS does this (dismount and change) for each volume only if the volume attribute is changing. This makes sense for GPT disks. But for MBR disks this attribute is shared by all the volumes on the disk. Hence, for another volume on the same MBR disk, VSS sees that the RO attribute is not changing and does not do the dismount.
1) Ensure all MBR Disks have only a single partition. In order to achieve this you should backup all data on the extra partition and then delete any extra partitions on the drive. You can use any product for the backup that doesn't use a hardware provider. Restore the data to the new drive. For drives that contain Windows, this requires reinstalling the operating system, because removing the system reserved partition removes the files necessary for booting.
2) Only use GPT disks. For disks that will contain Windows, GPT disks can only be booted from when using UEFI system. This will require removing all partitions from the disk. Configuring the hardware to support UEFI, and then doing a fresh install. For data disks, to convert an MBR disk to GPT please follow How To Convert MBR disk to GPT disk. This also requires that all data and all partitions be removed and deleted.
Article ID: 2853247 - Last Review: Sep 11, 2013 - Revision: 1