/ɡaɪd pɑːrˈtɪʃən ˈteɪbəl/
noun — "modern disk partitioning standard with large capacity support."
GUID Partition Table, often abbreviated GPT, is a modern partitioning scheme for storage devices that overcomes the limitations of the legacy MBR system. It supports disks larger than 2 TB, allows for virtually unlimited partitions (commonly 128 in practice), and includes redundancy and checksums to improve data integrity. GPT is part of the UEFI (Unified Extensible Firmware Interface) standard and is widely used in contemporary BIOS- and UEFI-based systems.
Technically, a GUID Partition Table stores partition information in a globally unique identifier (GUID) format. Each partition has a unique 128-bit GUID, a starting and ending LBA (Logical Block Address), a partition type GUID, and attribute flags. GPT structures also include a protective MBR at the first sector to prevent legacy tools from misidentifying the disk as unpartitioned.
A GPT disk layout typically consists of:
- Protective MBR: The first sector contains a standard MBR with a single partition entry spanning the entire disk, safeguarding GPT data from legacy tools.
- Primary GPT Header: Located at LBA 1, it contains the size and location of the partition table, disk GUID, and CRC32 checksum for header validation.
- Partition Entries: Immediately following the primary header, an array of partition entries (default 128) stores GUIDs, start/end LBAs, and attributes.
- Backup GPT Header and Partition Table: Located at the end of the disk, ensuring recoverability if the primary structures are corrupted.
Workflow example: when a system boots or mounts a GPT disk, the firmware or operating system reads the primary GPT header to locate the partition table. Each partition is identified via its GUID, and the OS uses this information to mount filesystems or prepare volumes for use. In case of corruption, the backup GPT header at the disk’s end can restore partition information, providing resilience absent in traditional MBR disks.
Practical usage includes modern operating systems requiring large disks, multi-boot configurations, and environments needing improved partition integrity checks. GPT enables flexible partitioning schemes for servers, workstations, and personal computers, while supporting advanced features like EFI system partitions and hybrid MBR/GPT setups for backward compatibility.
Conceptually, a GUID Partition Table is like a meticulously labeled map of a library: each section (partition) has a unique identifier, boundaries are precisely defined, and backup copies exist to prevent loss, ensuring efficient and reliable access to stored information.
See MBR, UEFI, Disk Partitioning.