Understanding Disk Partitions
42 out of 57 rated this helpful - Rate this topic
Published: October 22, 2009
Updated: June 28, 2011
Applies To: Windows 7, Windows Server 2008 R2
Note
This content applies to Windows 7. For Windows 8 content, see Windows Deployment with the
Windows ADK.
During an attended or unattended installation, you can divide your hard drive (for example, hard
disk drive or solid-state drive) into distinct sections called partitions.
In This Topic

Partition Structures

Partition Rules

System Partitions

Microsoft Reserved Partition (MSR)

Windows Partition Requirements

Recovery Tools

Changing the Disk Configurations During
Windows Setup

Recommended Disk-Partition Configurations
Partition Structures
The partition types must match the firmware of the computer. You can install Windows® 7 and
Windows Server® 2008 R2 on hard disks that are based on any of the following types of firmware:

Basic Input/Output System (BIOS). Uses the
Master Boot Record (MBR) partition structure.

Extensible Firmware Interface (EFI) Class 1.
Uses the GUID Partition Table (GPT) partition
structure.
1

Unified Extensible Firmware Interface
(UEFI) Class 2: Uses the GPT partition
structure. Also includes a compatibility support
module (CSM) that enables you to use BIOS
functions, including the MBR partition structure.
This module may be enabled or disabled in the
firmware.

Unified Extensible Firmware Interface
(UEFI) Class 3: Uses the GPT partition
structure.
To determine your system type, consult your hardware manufacturer.
Partition Rules
The partition structure is different on BIOS-based and UEFI-based computers.
BIOS-Based Computers
When you deploy Windows® to a BIOS-based computer, you must format hard drives by using an
MBR file system. Disks that use the GUID partition table (GPT) structure are not supported on
BIOS-based computers.
An MBR-based drive must meet the following conditions:

Each disk can have up to four standard
partitions. Typically, these standard partitions
are designated as primary partitions. You can
use primary partitions to store files.
For information about creating additional
partitions beyond this limit, see BIOS: To use
more than four partitions later in this section.

The computer must boot to the active partition.
You can designate only one primary partition as
active.
On Windows® 8 and Windows Server® 2012
configurations, the active partition is typically a
separate partition that is called a system
partition.

Each partition can have a maximum of 2
terabytes (TB) of space. Software tools to extend
the visible partition space beyond 2 TB are not
supported on BIOS because they can interfere
2
with application compatibility and recovery
software solutions.
The following diagram shows the default Windows 7 and Windows Server 2008 R2 partition
structure:
BIOS: To use more than four partitions
1. Designate one of the four standard partitions as
an extended partition.
An extended partition is a special partition that
can be divided into additional partitions called
logical partitions. You can divide the extended
partition into as many logical partitions as can fit
on your disk.
An extended partition cannot store files; it can
store only logical partitions.
2. Add logical partitions to the drive.
Logical partitions can store data.
The following diagram illustrates an example of a disk partition structure that includes primary,
extended, and logical partitions:
UEFI-Based Computers
3
When you deploy Windows® to an EFI-based or UEFI-based computer, you must format the hard
disk drive or other persistent storage device that includes the Windows partition by using a GUID
partition table (GPT) file system. Additional drives might use either the GPT or the master boot
record (MBR) file format.
A GPT-based drive might include the following partitions:

An EFI System Partition (ESP)
Each bootable drive must contain an ESP. The
computer boots to this partition.
For Advanced Format Generation One (4-KBper-sector) drives, the minimum size of this
partition is 260 MB.
For earlier 512-byte-per-sector drives, the
minimum size of this partition is 100MB.

A Microsoft® Reserved Partition (MSR)
We recommend that you add an MSR to each
drive for disk management. The MSR is a
reserved partition that does not receive a
partition ID. It cannot store user data.
The size of an MSR partition is 128 MB.

Up to 128 primary partitions
You can use primary partitions to store files and
utilities.
Each bootable drive must contain an operating system, such as Windows.
Each partition can have a maximum of 18 exabytes (EB) of space.
The following diagram shows the default Windows 7 and Windows Server 2008 R2 GPT-based
partition structure:
4
For more information about UEFI disks and hard disk partitions, see The Windows and GPT FAQ.
The computer will boot to the Extensible Firmware Interface System Partition (EFI System
Partition, or ESP).
System Partitions
You can use system partitions to:

Manage and load other partitions. If there are
multiple operating systems, for example,
Windows 7 and Windows Vista®, the computer
displays a list of operating systems. The user can
then select which operating system to use.

Use security tools, such as
Windows® BitLocker® Drive Encryption.

Use recovery tools, such as Windows Recovery
Environment (Windows RE).
In Windows 7 and Windows Server 2008 R2, system partitions do not appear in the list of available
drives, although they can appear in tools such as Computer Management.
System Partition Requirements
Basic system partition requirements are:

Must have at least 100 megabytes (MB) of hard
drive space.

Must have enough free space to create shadow
copies of the partition.
o
If the partition is less than 500 MB, it
must have at least 50 MB of free space.
o
If the partition is 500 MB or larger, it
must have at least 320 MB of free space.
o
If the partition is larger than 1 gigabyte
(GB), we recommend that it should have
at least 1 GB free.
Note
Aside from the Windows RE tools, we recommend that you place no other files on the
system volume, and that you discourage end users from storing files on this partition, to
avoid filling up this space.
5

Must not be an encrypted partition.

Must be configured as the active partition.

BIOS/MBR: May be formatted as either FAT32
or NTFS.
UEFI/GPT: Must be formatted as FAT32 .
Note
To discourage users from accidentally modifying or deleting the partition:

Identify the partition as a utility partition. Utility partitions do not receive a drive letter. To
identify the partition as a utility partition, set the unattended setting, Microsoft-WindowsSetup\DiskConfiguration\Disk\ModifyPartitions\ModifyPartition\TypeID to 0x27
on BIOS-based systems, or de94bba4-06d1-4d40-a16a-bfd50179d6ac for UEFI-based
systems.

Add a label to the partition. This helps users identify the partition when viewing the disk
with tools such as Computer Management.
Additional requirements for BitLocker
BitLocker increases protection for your computer by running Windows in a separate, encrypted data
partition.
When BitLocker is installed, the following are additional requirements for the system partition:

The partition must be separate from the
Windows partition.
For more information, see Understanding BitLocker Drive Encryption.
Additional requirements for Windows RE
Windows RE can help users recover from critical system failure.
You can install Windows RE tools in the system partition, in the Windows partition or in a separate
recovery partition.
When Windows RE tools are installed on the system partition, the following are additional
requirements for the combined partition:

The partition must be physically located in front
of all user partitions.
6

Must have an additional 200 MB of hard drive
space for Windows RE tools.
Example: System + Windows RE tools =
300 MB

Must not be used to store user files.
When Windows RE tools are installed on a separate partition, the following are additional
requirements for the Windows RE partition:

Must have enough free space to create shadow
copies of the partition.
o
If the partition is less than 500 MB, it
must have at least 50 MB of free space.
o
If the partition is 500 MB or larger, it
must have at least 320 MB of free space.
o
If the partition is larger than 1 GB, we
recommend that it should have at least
1 GB free.
o
Must not be used to store user files.
For more information, see Understanding Windows Recovery.
For information about deploying Windows RE, see Deploy a System Recovery Image.
Additional requirements for Advanced Format Generation One (4-KB-per-sector) drives
The minimum size of the system partition on an Advanced Format Generation One drive is 260
MB.
Microsoft Reserved Partition (MSR)
The MSR is used on UEFI/GPT systems, to support software components that formerly used hidden
sectors.
The MSR partition must:

Have 128 MB of hard drive space.

Be located before the Windows operatingsystem partitions.
For more information about MSR partitions, see Windows and GPT FAQ
7
Windows Partition Requirements
The Windows partition must:

Have at least 15 gigabytes (GB) of hard drive
space, including 700 MB of free space during
Windows Setup.
Recovery Tools
To help end users recover from critical system failures, you can include system-recovery tools on
your system. In the case of a system failure, you can configure the computer to fail over to the
recovery tools, to help end users repair or reinstall Windows.
The requirements for a recovery partition will vary, depending on the recovery environment you
intend to implement.
Note
Consider installing recovery tools in either the system partition or a separate partition, to enable end
users to repair or reinstall Windows without deleting the recovery tools.
To discourage users from accidentally modifying or deleting the partition:

Identify the partition as a utility partition. Utility partitions do not receive a drive letter. To
identify the partition as a utility partition, set the unattended setting, Microsoft-WindowsSetup\DiskConfiguration\Disk\ModifyPartitions\ModifyPartition\TypeID to 0x27
on BIOS-based systems, or de94bba4-06d1-4d40-a16a-bfd50179d6ac for UEFI-based
systems.

Add a label to the partition. This helps users identify the partition when viewing the disk
with tools such as Computer Management.
Changing the Disk Configurations During Windows Setup
You can change the default disk configurations by using any of the following options:

Use Windows System Image Manager
(Windows SIM) to configure settings. For more
information on creating hard disk partitions, see
Create BIOS-based Hard-Disk Partitions by
Using Windows SIM and Create UEFI-based
Hard-Disk Partitions by Using Windows SIM.

From Windows PE, or another environment, use
the Diskpart command to create and modify
8
partitions. For more information on Diskpart,
see Apply Images by Using ImageX.

During an attended installation, click Advanced
while the Disk Configuration user-interface
page is displayed, and follow the on-screen
instructions to set up partitions.
Recommended Disk-Partition Configurations
The following table includes links to topics that include recommended disk-partition configurations.
Recommended BIOS-Based Disk-Partition Configurations BIOS-based systems
Recommended UEFI-Based Disk-Partition Configurations UEFI-based systems
See Also
Concepts
Understanding BitLocker Drive Encryption
Deploy a System Recovery Image
9