Today, I set up a new laptop for a user. As a standard practice, we always BitLock the laptops that we issue out. I was in the middle of copying the user’s data over and it kindly hung while I was BitLocking at the same time. The files finally copied over, and I went to My Computer and seen there was only 6GB left of a 500GB hard drive, and I only copied 3GB of data over! I jsut knew there was something wrong with the file system of the hard drive since it hung.
After doing some digging, I found that BitLocker uses up all but 6BG of your hard drive space UNTIL its done bitlocking. After it is done, all the free space will be shown as free again.
But why does it do this?
Because it is also encrypting the free space for security reasons! Since when you delete a file, it is not really removed from the hard drive, BitLocker encrypts the free space so that none of these files can be recovered. You can read a more technical description here!
http://blogs.technet.com/b/bitlocker/archive/2006/07/08/unallocated.aspx