So you are running a software RAID0 in the guest OS? Even though it should be possible to migrate the virtual disks online, I would be extremely careful in this case and rather either schedule downtime for the migration or - my personal preference - migrate the data to a new virtual disk (using e.g. robocopy in case of Windows) to get rid of the SW RAID. If you are still running an ESX/ESXi version prior to 5.x with the VMFS3 file system, you will need to create a datastore with an 8MB blocksize in order to create a 2TB (max. 2,032 GB if you want to be able to take snapshots) virtual disk.
In any case, ensure you have an up-to-date backup before doing this!
André