Bitlocker Drive Space Anomaly

While Bitlocker is encrypting your drive, the program automatically locks your entire drive except for 6GB. This is normally not a problem, but can be an issue if you are doing significant copying to the disk being encrypted. The following verbiage from a TechNet article describes this “feature” and describes how to temporarily pause the encryption in case you need to do work that requires more than 6GB on the disk. [more]

Why does it appear that most of the free space in my drive is used when BitLocker is converting the drive?

BitLocker cannot ignore free space when the drive is being encrypted because unallocated disk space commonly contains data remnants. However, it is not efficient to encrypt free space on a drive. To solve this problem, BitLocker first creates a large placeholder file that takes most of the available disk space and then writes cryptographic material to disk sectors that belong to the placeholder file. During this process, BitLocker leaves 6 GB of available space for short-term system needs. All other space, including the 6 GB of free space not occupied by the placeholder file, is encrypted. When encryption of the drive is paused or completed, the placeholder file is deleted and the amount of available free space reverts to normal. A placeholder file is used only on drives formatted by using the NTFS or exFAT file system.

If you want to reclaim this free space before encryption of the drive has completed, you can use the Manage-bde command-line tool to pause encryption. To do this, open an elevated command prompt and type the following command, replacing driveletter with the letter of the drive you want to pause encryption on:

manage-bde –pause driveletter :

When you are ready to start encrypting the drive again, type the following command:

Manage-bde –resume driveletter :

Networking Windows 7 BitLocker