When you prepare any drive or volume to be used by Windows Server 2008, you must first partition the disk and then format the disk. Partitioning is defining and dividing the physical or virtual disk into logical volumes called partitions. Each partition functions as if it were a separate disk drive.
Windows Server 2008 supports two types of disk partitioning styles:
- Master Boot Record (MBR)
- GUID partition table (GPT)
MBR disks have been used as standard equipment on IBM-compatible personal computers since the days of MS-DOS. MBR disks support volume sizes of up to two terabytes (TB) and allow up to four primary partitions per disk. Alternatively, MBR disks support three primary partitions, one extended partition, and an unlimited number of logical drive letters.
Windows Server 2008 includes support for global unique identifier—or GUID—Partition Table (GPT) disks in cluster storage. GPT disks were introduced with computers equipped with Intel Itanium-based processors and the Extensible Firmware Interface (EFI) as an alternative to a Basic Input/Output System (BIOS) as the interface between the computer’s hardware devices, its firmware, and the operating system. GPT provides a more flexible mechanism for partitioning disks than the older MBR partitioning scheme that has been common to PCs. GPT disks support volume sizes up to 18 exabytes (EB) and can store up to 128 partitions on each disk. Eighteen exabytes are roughly equivalent to 18 billion gigabytes. Critical system files are stored on GPT partitions, and GPT disks store a duplicate set of partition tables to ensure that partitioning information is retained.