How can I configure a Mac partition as a disk in a VM?

For testing purposes I would like to configure a partition from my Mac host disk as a secondary disk in a Windows virtual machine. That Mac partition is free and will ideally be formatted by the Windows VM.

I see the choice of attaching a BootCamp partition. It does not work and fails configuring it in the VM. I suppose this mode wants a real BootCamp partition, that is one with a Windows installed on it. I don't want to install Windows on that partition, I just want a NTFS partition, native on the Mac disk, seen as a Disk D: or whatever in my virtual machine.

The purpose? Especially testing if, along side scsi setting in the VM configuration the I/O performances over that partition might be better than on a fixed size (non growing, pre-allocated) virtual disk on the host filesystem.

Parallels? Is it even worth desiring to test such a configuration? Maybe you know from start that it won't bring additional performance? Is this possible now (without loosing my time installing a Windows though BootCamp which I won't use)? Is it scheduled for a later release of the product?

 

To better describe what I'm trying to do, please consider these commands and results. Thanks.

$ prlctl list -a
UUID STATUS NAME
{88353396-4481-486d-8660-e0a3e75ba88c} stopped Test Lab XP
{f45f8e29-033a-4b2c-b136-0b4bed72d419} stopped Windows 7

$ prlctl server info
...
Version: Desktop 4.0.3844.408728
OS: Mac OS X 10.5.7
...
Hardware info:
hdd WDC WD3200BJKT-00F4T0 /dev/disk0
hdd-part /dev/disk0s2
hdd-part FAT32 /dev/disk0s3
hdd-part EFI System Partition /dev/disk0s1

$ prlctl set "Test Lab XP" --device-add hdd --device /dev/disk0s3 --iface scsi --position 1 --enable
Creating hdd1 (+) scsi:1 real='WDC WD3200BJKT-00F4T0' device=</dev/disk0s3>
Unable to commit Vm configuration: Failed to configure the Boot Camp partition's hard disk.
Failed to configure the virtual machine.

Why does this command fails by telling me it couldn't configure the Boot Camp partition ? This is NOT a boot camp partition, this is only a partition FAT32 formatted created through Mac OS X disk utility. There is NO Windows OS installed on the partition, it is empty and intended to be used as a data disk not as a bootable Boot Camp partition with windows on it.