I've just completed upgrading my system to Lion. As I have gathered up a lot of files from old applications and a Mail folder which was far too big, I decided to erase my hard drive and install Lion fresh. Of course before I did this I did a backup with Time Machine, and also with Carbon Copy Cloner.
Although CCC might have been slightly quicker, I restored all my user files (~/Documents/, ~/Photos/, etc) using my Time Machine backup. Once this was complete, I turned Time Machine back on, and it proceded to do a full backup of the entire drive. Not idea, since my close-to-400GB of user files hadn't actually changed, but fair enough, considering I had wiped the hard drive and it was backing up a brand new system - which I'm sure it's seeing the same as it would a new drive.
Before I installed Lion, I also included an external hard drive in my Time Machine backup. For some reason, Time Machine in Lion iss wanting to back up the entire drive again. Considering I've got about 300GB of files on the drive this seems really redundant to me - it's space which I could use for backing up files which had actually changed!
The strange thing is, I could still navigate the pre-Lion backups of this drive. I went back to the oldest backup and chose "delete all backups of "Drive Name", hoping this would free up a few hundred GBs of space on my Time Machine drive. Sadly it didn't - while user access to the backups has dissapeared, the free space on my Time Machine drive hasn't increased at all.
Has anyone else experienced this kind of activity with Time Machine after upgrading to Lion?