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GPT disk / GPT partition

A GPT disk is a disk containing a GPT partition table.

The GPT table is stored in the 33 sectors immediately following the MBR (LBA 1 to 33). Additionally a backup of the GPT table is stored at the end of the disk. To prevent an unintentional overwriting of GPT partitions by MBR partition managers the whole disk space (except for the MBR) is marked as occupied by the so-called GPT protective partition. Since the MBR table contains only 32 bit sector numbers the GPT protective partition is limited to a size of 2 TiB.

The following table summarizes the main differences between MBR and GPT partitions.
Parameter MBR GPT
Sector numbers 32 bit 64 bit
Max. disk size 2 TiB 8 x 1012 TiB
Partition ID ID with 8 bit GUID with 128 bit
Partitions per disk 4 pri. 128
Check sum no yes

The drawing below shows the main elements of a GPT disk: MBR with reference to GPT protective partition, primary and backup GPT table with references to GPT partitions.
GPT partition