Wednesday, July 16, 2014

What is the System Reserved Partition and Can You Delete It?

Windows 7 and 8 create a special “System Reserved” partition when you install them on a clean disk. Windows doesn’t assign a drive letter to these partitions, so you’ll only see them when you use Disk Management or similar utility.
The System Reserved Partition was introduced with Windows 7, so you won’t find it on previous versions of Windows. The partition is also created on Windows Serer 2008 R2 and newer Server versions of Windows.

What Does the System Reserved Partition Do?

This partition contains two important things:
  • The Boot Manager and Boot Configuration Data : When your computer boots, the Windows Boot Manager starts up and reads the boot data from the Boot Configuration Data (BCD) Store. Your computer boots the boot loader off the System Reserved partition, and it boots Windows from your system drive.
  • The startup files used for BitLocker Drive Encryption: If you ever decide to encrypt your hard drive with BitLocker drive encryption, the System Reserved partition contains the necessary files for starting your computer. Your computer boots the unencrypted System Reserved partition, and it will decrypt the main encrypted drive and boot the encrypted Windows system.
The System Reserved partition is essential if you want to use BitLocker drive encryption, which can’t function otherwise. Important boot files are also stored here by default, although you could store them on the main Windows partition if you preferred.

When Windows Creates the System Reserved Partition

The System Reserved partition consumes 100 MB of space on Windows 7 and 350 MB of space on Windows 8. It’s created during the Windows installation process when you partition your drives.
When you use the graphical partition manager in the Windows installer to create your Windows partition in unallocated space on a drive, you’ll receive a message saying, “To ensure that all Windows features work correctly, Windows might create additional partitions for system files.” Windows will usually create a System Reserved partition in the unallocated space before the main system partition.

Can You Delete the System Reserved Partition?

You probably shouldn’t mess with this partition — it’s easiest to just leave it be. Windows hides it by default instead of creating a drive letter for it. Most people will never notice they have a System Reserved partition, and Windows will only show it to you when you use disk-partitioning software. This partition is mandatory if you use BitLocker or want to use BitLocker in the future. On Windows Vista, a drive had to be specially set up with such a partition after the installation process — now every drive is made ready for BitLocker while installing Windows.
If you don’t want this partition on your drive, the ideal thing to do is prevent it from being created in the first place. Rather than create a new partition in unallocated space from within the Windows installer, you can create a new partition consuming all the unallocated space with another disk-partitioning tool. Point the Windows installer at the partition you created and Windows will happily continue — it won’t attempt to resize your partition and create a System Reserved partition. The Windows installer will accept that there’s no room for System Reserved partition and install Windows onto a single partition. Bear in mind that you’re not saving an entire 100 MB or 350 MB by doing this, as the boot files will instead be installed on the main system partition.
To do this, you’ll need to use any disk-partitioning software except the graphical one in the Windows installer. However, you can actually do this from within the Windows installer. Just follow the following steps:
  • Press Shift+F10 while installing Windows to open a Command Prompt window.
  • Type diskpart into the Command Prompt window and press Enter.
  • Create a new partition in the unallocated space using the diskpart tool. For example, if you have a single drive in the computer and it’s completely empty, you can just type select disk 0 and then create partition primary to select the first disk and create a new partition using the entire amount of unallocated space on the drive.
  • Continue the setup process. Select the partition you created earlier when you’re asked to create a partition.
It may be possible to remove a System Reserved partition after installing Windows. You can’t just delete the System Reserved partition. Because the boot loader files are stored on it, Windows won’t boot properly if you delete this partition. To delete the System Reserved partition, you’d first have to move the boot files from the System Reserved partition onto the main Windows system drive.
This is harder than it sounds. It will involve messing with the registry, copying various files between drives, updating the BCD store, and making the main system drive the active partition. On Windows 8, it will also involve disabling and then re-enabling the Windows recovery environment. You’ll then have to remove the System Reserved partition and enlarge your drive.
This may be possible, and you’ll find some guides walking you through the process on the web. However, it’s not officially supported by Microsoft and we don’t recommend it. You’ll gain a very tiny bit of space — less than the 100 MB or 350 MB used by the System Reserved partition — at the cost of potentially messing up your operating system and losing the ability to use BitLocker drive encryption.
For reference, here’s why you shouldn’t just delete the System Reserved partition. We used the GParted partition editor on an Ubuntu live CD to delete the System Reserved partition and made the main Windows 8.1 partition bootable with no attempt at copying the boot files. We saw a message saying our Boot Configuration Data was missing, and that we’d have to repair our computer with Windows installation media.

This partition may look like it’s cluttering your drive and wasting space, but it performs important functions and removing it will free up almost no space. You should learn to ignore the partition — if you really don’t want it, you should prevent it from being created while installing Windows.

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