Does using the new FileVault use up less disk space than Legacy FileVault?

Solution 1:

The two technologies share nothing except the name and cannot be directly compared. The old Filevault created a spare bundle image file for your home folder, which was encrypted. The new one simply encrypts the whole drive in a way that is invisible to the user.

If anything there may be a slight overheard to managing a sparsebundle which will not be there for whole disk encryption, but I doubt that it will be significant enough to make it a part of your decision to use it or not.

Solution 2:

As Stuffe said, the two versions of FileVault are based on completely different technologies. The implications for disk space, however, are not trivial. The new FileVault is block level full-disk encryption, and as such exists completely outside the filesystem, and therefore it takes up zero filesystem space. It might take up a small amount of actual disk space, but the number you see when you "Get Info" your disk in Mac OS X will never be affected by Lion's new FileVault.

The old FileVault, however, was implemented within the filesystem - like Stuffe said, it was an encrypted sparsebundle for every user. This had implications such that if lots of space were allocated to the sparsebundle while it was mounted (while the user was logged in) it could only be reclaimed when it was unmounted (when the user logged out). I'd been in that situation many times myself, knowing that running of of space on my drive meant I had not only to trash some files but go through the agonizing process of logging out and waiting who knows how long to let Mac OS X reclaim some of that space. The new FileVault in Lion removes all of that.

Solution 3:

Yes - the overhead required by the new file vault encryption takes less space than the old FileVault implementation. Often ten or more gigabytes less space on drives in the 250 to 500 GB size and normal moderate file usage of photos, music and light video storage needs.

The new implementation uses only a fixed amount of space to handle the storing of the keys needed to decrypt the core storage. Most drives reserve 650.0 MB of space for the recovery HD that is created (or used) when you encrypt a whole disk in Lion using File Vault.

The older implementation stored the user folder only in a sparse disk image which resulted in slightly less initial overhead to create the key storage space and the initial directory to track the files within the sparse disk image. However, in use, files are marked for deletion and not actually deleted until a later "reclaim" or "compact" the storage and reclaim space that was used by this method of encrypting the files. It was not uncommon to have tens of gigabytes of space in normal situations where users had File Vault enabled on pre-Lion OS.

When you switch to the new encryption - you no longer need any compact time or delay. The overhead is fixed and constant. This alone is a great benefit even before you take in account how the new logical volume stops breaking apps since the encryption is totally transparent to all applications.

As usual, John Siracusa's review has a great dissection of the changes that Lion made to FileVault.

• Mac OS X 10.7 Lion: the Ars Technica review - File system changes in Lion

In addition the new implementation can be enabled and disabled on the fly and the machine will handle encryption/decryption without needing double the space of the files to hold the intermediate files during decryption. With the old FileVault you could literally be stuck and unable to turn off decryption if the free space was smaller than the folder payload size. You couldn't decrypt in place and instead needed to copy the data out piecemeal or get a spare drive to hold the decrypted contents when you turned FileVault off.