Time Machine: How can less files occupy more space??

[baslotto]

Hi all.

Sorry if this topic has been discussed previously, I did a little research but I couldn't find anything about it.

I just noticed that after moving stuff around Time Machine detected about 40 new GB of files to back up.
I got a little surprised so I decided to erase some files from an external HD that was included in my backups. I believe I erased some 60GB of files that I didn't need.

Next thing I did was a "Back Up Now" in TM.
I now had 127.8 GB to back up!!!

How can this be?

As I said, if this has been discussed previously please re-direct me toward the thread, I'm a good reader but a bad searcher.

Thank you all.

Bas.

*edit*: I have to say that erasing some files I also re-organized the ones that I wanted to keep, so to have less folders in the first level of my external HD. I went from 15 folders down to 4 (ex.: putting all the music folders in a folder named "Music to Backup" and so on).

I'm still hoping for an answer.
Probably nobody knows it, including Cupertino...

 

[pjrobertson]

Time Machine backs up all changed files since the last backup.
I'm guessing that moving the files meant they all needed to be backed up again.

The easiest thing to do would be to erase your Time Machine Disk and start again.
It is a little strange though...
I've used 40GB of my internal hard drive, and only 40GB of my TM hard drive.

 

[killerwhack]

Timemachine works on wrap around mode

As the allocated space for timemachine becomes full, timemachine begins to erase the oldest changes.

If you allocated the entire disk for timemachine, then this will not happen until the entire disk is full. It will be interesting to see how far back in time you can go once the disk is full. The larger the disk (or allocation) the farther back you will be able to see.

I went for broke and got a 2 terabyte mybook from Western Digital (WD).

 

[wilfried]

Rearranging the files accounts for the large second backup. When you move a file to a new folder, Time Machine treats it as a new file, and backs it up again (this is considered best practice, rather than try to have Time Machine decide if the file was in fact identical to another file it had seen elsewhere). Deleting files from your hard drive will not shrink the size of the backup; they deleted files stay in Time Machine, so you can go back to them should you need to (the whole point is to allow you to retrieve deleted files, or older versions of changed files, hence the name Time Machine...). Time Machine will grow with each backup, and never shrink (unless you manually delete files from your backup) until it fills the hard drive.

 

[baslotto]

Thank you very much, I really appreciate your feedback.
I noticed I can't take stuff off my backups in TM because it chops files up in many folders making them impossible to recover outside the interface Time Machine (pretty much like BitTorrent, correct me if I'm wrong) so I guess the only way to make my hard drive last as long as I want is to erase and "restart" TM with a new fresh backup of my files (only today I occupied 3 GB of "nothing at all"!).
This thing is more high maintenance than Britney Spears!
Great tool though, I thank Apple for making this happen.

Bas