Coming from a perspective of the P2V, the physical server will be converted into the attached storage of the ESX host. How would connecting that server into the iscsi fabric speed up the transfer, traffic still has to go through the ESX host.
Is that 3 partitions of 1.8 TB each or combined?
The block size of your datastores will limit the size of the file / vmdk that can be create for the conversion.
As far as coverting 2 TB, that is going to take a while.
Good luck,