If you have a high end version of either Windows Vista or 7, you might have observed that there is an encryption option called ‘BitLocker Drive Encryption’ by default. As the name suggest, you can protect a drive (either your system hard drive partition or an external hard drive/ USB) by encrypting it and saving it behind a Password you set or other similar ways. For the drives, though, you will not have the option to use BitLocker, such as those drives that contain System files. You can right click on any drive to see if the ‘Turn on BitLocker’ is enabled or not.
Before you do that, you may want to know the time it takes to encrypt the drive. Well, I just tried using BitLocker drive encryption to encrypt my external Seagate 500GB Hard drive, just to see how that stuff works, and it took a hell lot of time. This external hard disk only has some 50GB of data and the rest is all empty.
Here it is, it took a neat ‘One Hour’ to complete ‘5% Encryption’.
Because BitLocker doesn’t encrypt the free space, you can simply extrapolate this time to 20 Hours for complete encryption (100%). So effectively, it took 1 Hour to Encrypt 2.5GB of Data (5% of 50GB Data). (As Little Timmie points out in the comments, BitLocker encrypts empty space too; not just the part filled with data). During the encryption process you may observe that the Disk space is shown as 95% used, that is normal.
Since I talked about extrapolating, you can understand that I cancelled the encryption process. Well, cancelling isn’t the right word since there is no option to cancel but only ‘Decrypt’. You have to go to Control Panel-> System and Security->BitLocker drive encryption and select ‘Turn off Encryption’ for the appropriate drive. It will then Decrypt the drive, and, it took the same time, One Hour to Decrypt 2.5GB of Enrypted data.
But one good thing here, apart from the encrypting feature of course, is that you can ‘Pause’ and continue encryption or decryption as and when you want. You can Switch off your computer too, and the process would resume as soon as you power On your PC or connect your USB device.