What is the Windows Server 2008 R2 / Windows 7 System Reserved Partition?

When you install Server 2008 R2 (or Windows 7) to a fresh partition, sometimes you’ll receive the following message:

Then, after installation, when you inspect the disk configuration in Disk Management, you see this partition named System Reserved. It’s 100MB in size and it doesn’t have a drive letter. This 100MB partition is where the Windows boot loader resides. This is needed if you’re going to implement Bitlocker. Installation now by default, prepares the installation for Bitlocker. This has changed from the Windows Vista / Server 2008 configuration where you have to prepare a drive to support Bitlocker. The installation does not install Bitlocker, it just configures the server in the event you want to enable Bitlocker. This is a much better plan than before.

The guidance for Vista, Windows Server 2008 was to create a 1.5GB drive to support the boot loader. In Windows 7 and R2, this drive now only needs to be 100MB. Please do not mess with this partition unless you know what your doing (really). Messing this up will render your OS unbootable. The good news is that the repair tools in the install media can usually detect when the System Reserved partition has been damaged and will repair it. If you’re not going to use Bitlocker, don’t worry, it’s only 100MB, and it is still beneficial in separating the boot loader from the OS.

Did you notice how warning during setup says Windows might create additional partitions? If you’re not installing Server 2008 R2 (or Windows 7) on the boot partition, the install will probably not create the 100MB partition, it will probably put the boot loader on the boot partition. Say you are setting up a dual boot between Windows Server 2003 and Server 2008 R2. If Server 2003 is installed on Disk 0 of your server and you’re going to install R2 on Disk 1 of the machine, R2 will install the boot loader on the Server 2003 partition and setup a dual boot scenario during the install process.

Tags: Windows Server 2008 R2,System Reserved,To ensure that all Windows features work correctly,Windows might create additional partitions for system files