The guest operating system running in a virtual machine will typically require access to disk storage both to contain the system files and any user data. The first requirement is that the storage to be used by the virtual machine must be accessible to the host system. In terms of storage access, Hyper-V supports ''Direct Access Storage (DAS) drives including IDE, SATA, SCSI and SAS, and ''Storage Area Network'' standards such a fiber channel and iSCSI.
Assuming that the storage is connected to the host system in some way there are two choices as to how a virtual hard disk is made available to the virtual machine:
[[Image:hyper- '''V_configure_virtual_hard_disk.jpg|Specifying the Virtual Hard Disk (VHD)''' - The virtual hard disk created as for a file which resides on a storage colume which is accessible to the host server. Disks can be ''dynamic expanding'' (starts small and grows as space is required) or ''fixed'' in size. The maximum size of VHD is 2040GB.Virtual Machine]]
- '''Pass-through disk''' - A pass-through disk assigns a physical disk drive to the virtual machine enabling the guest operating system to perform raw read and write actions on the disk. Hyper-V imposes no constraints on the size of a pass-through disk.
Although Assuming that the storage is connected to the host system in some way, there are a number of choices as to how a virtual hard disk is made available to the virtual machine: - '''New Virtual MachineHard Disk (VHD)'' wizard does not provide ' - The virtual hard disk created as a file which resides on a storage volume which is accessible to the host server. Disks can be ''dynamic expanding'' (starts small and grows as space is required) or ''fixed'' in size. The maximum size of VHD is 2040GB. - '''Existing Virtual Hard Disk (VHD)''' - A virtual machine can be configured to use a pre-existing disk image file. - '''Passthrough disk''' - A passthrough disk assigns a physical disk drive to the virtual machine enabling the guest operating system to perform raw read and write actions on the disk. Hyper-V imposes no constraints on the size of a pass-through disk. To configure a passthrough disk, select the option to''Attach a virtual hard disk later''.
