Past editions of operating systems used 32-bit addressing schemes, which effectively limited support for single disk devices to 2 terabytes (TB) or less. The GUID Partition Table (GPT) is a replacement for the older MBR. Currently, x86-based computer systems use a legacy BIOS that will not support the use of GPT drives as a boot device. However, depending on the operating system, support has been added for GPT drives as additional data volumes only.
Based on the limitations around booting to drives larger than 2TB in size and the other OS limitations, Dell will not ship any servers with a RAID configuration larger than 1.8TB. If an array greater than 1.8TB is specified in the system configuration, then the system will ship with several RAID slices that are each 1.8TB or less.
This Dell Community forum post details the process of creating RAID arrays larger than 2TB:
Instructions to convert a disk to a GPT Disk for one large > 2TB partition (Win2k3 SP1):