EFI System Partition

When I started a system image backup of a Windows 8.1 Professional system to an external USB drive, one of the 3 partitions identified on the internal hard disk drive was labeled "EFI System Partition".

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Windows 8.1 Confirm Backup Settings

Disk Management, which can be accessed by right-clicking on the Windows Start button and selecting Control Panel, System and Security, Administrative Tools, and then Computer Management, which will show Disk Management beneath Storage, showed the partition as a 100 MB partition with a status of "Healthy (EFI System Partition)" (image).

So what is stored on the "EFI System Partition"? According to the Wikipedia EFI System partition article:

The EFI System partition (ESP) is a partition on a data storage device that is used by computers adhering to the Unified Extensible Firmware Interface (UEFI). When a computer is powered up and booted, UEFI firmware loads files stored on the ESP to start installed operating systems and various utilities. An ESP partition needs to be formatted with one of the FAT file system variants.

ESP contains the boot loader programs for all installed operating systems (which are contained in other partitions on the same or other storage device), device driver files for devices present in a computer that are used by the firmware at boot time, system utility programs that are intended to be run before an operating system is booted, and data files such as error logs.

UEFI is the successor to the venerable BIOS used in older PCs. The article also notes that the partition must be formatted with either the FAT12, FAT16, or FAT32 file systems and that The globally unique identifier (GUID) for the EFI System partition in the GUID Partition Table (GPT) scheme is C12A7328-F81F-11D2-BA4B-00A0C93EC93B, while its ID in the MBR partition table scheme is 0xEF. I checked the partition file system with the diskpart command, which showed it was using the FAT32 file system. The type listed for the partition by diskpart matched the referenced GUID.


Microsoft DiskPart version 6.3.9600

Copyright (C) 1999-2013 Microsoft Corporation.
On computer: USERPC

DISKPART> select disk 0

Disk 0 is now the selected disk.

DISKPART> select partition 2

Partition 2 is now the selected partition.

DISKPART> detail partition

Partition 2
Type    : c12a7328-f81f-11d2-ba4b-00a0c93ec93b
Hidden  : Yes
Required: No
Attrib  : 0X8000000000000000
Offset in Bytes: 315621376

  Volume ###  Ltr  Label        Fs     Type        Size     Status     Info
  ----------  ---  -----------  -----  ----------  -------  ---------  --------
* Volume 3                      FAT32  Partition    100 MB  Healthy    System



  1. EFI System partition
    Date accessed: December 27, 2014
    Wikipedia, The Free Encyclopedia
  2. DiskPart Command-Line Options
    Microsoft TechNet
  3. HTG Explains: Learn How UEFI Will Replace Your PC’s BIOS
    By: Yatri Trivedi
    Published: March 25, 2011
    How-To Geek