GUID partition table

Instead of a BIOS, computers with the Intel Itanium family of processors use the Extensible Firmware Interface (EFI) between the computer's firmware, hardware, and the operating system. EFI includes a new disk partitioning style, the GUID partition table (GPT).

Compared to the master boot record (MBR) disk partitioning style, which supports volumes up to 2 terabytes in size and up to 4 primary partitions per disk (or three primary partitions, one extended partition, and unlimited logical drives), GPT supports volumes up to 18 exabytes in size and up to 128 partitions per disk. Unlike MBR partitioned disks, data critical to platform operation is located in partitions instead of unpartitioned or hidden sectors. In addition, GPT partitioned disks have redundant primary and backup partition tables for improved partition data structure integrity.

Disk Management describes disks with the GUID partition table (GPT) partitioning style as GPT disks and disks with the master boot record (MBR) partitioning style as MBR disks. You can perform the same tasks on GPT disks as you can on MBR disks with the following exceptions:

GPT disks are supported only by Windows XP 64-Bit Edition. You cannot move GPT disks to computers running the 32-bit versions of Windows XP. From Disk Management on computers running a 32-bit version of Windows XP, GPT disks appear as basic MBR disks with a single partition covering the whole disk, but the data on the partition cannot be accessed.

The operating system loader and boot partition must reside on a GPT disk. Other hard disks can be either MBR or GPT.

You can have both MBR and GPT disks in a single dynamic disk group. You can also have a mix of basic GPT and MBR disks, which are not part of disk groups.

You can convert an MBR disk to a GPT disk and vice versa only if the disk is empty.

You cannot use the GPT partitioning style on removable media, detachable disks that use universal serial bus (USB) or IEEE 1394 (also called FireWire) interfaces, or on cluster disks that are connected to shared SCSI or Fibre Channel buses used by the Cluster service.

You can create partitions on basic GPT disks using the EFI firmware utility diskpart.efi, the diskpart.exe command-line utility, or Disk Management in Windows XP 64-Bit Edition.

In a disaster recovery scenario, see the manufacturer's documentation that came with your computer for recreating or restoring a GPT disk.

For more information about DiskPart.exe, see DiskPart For more information about the Disk Management snap-in, see Disk Management overview For more information about diskpart.efi, see the Intel Web site.

For more information about managing GPT and MBR disks, see Extensible Firmware Interface (EFI)

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