You are using Serial Attached SCSI (SAS) Storage to provide volumes for Hyper-V Virtual Machines. When the volume has a size over 2 TB you are required to create this as a GPT Disk. You attach this disk to a Hyper-V Virtual Machine using the virtual SCSI Adapter.
You may experience a problem when the Volume is automatically checked during start of the VM by chkdsk, or when you manually start a chkdsk against such a volume. Chkdsk may hang in this scenario.
We are currently investigating this isse.
To workaround this problem, connect the SAS Passthrough disk to a Virtual IDE Channel instead.