How does Time Machine work?

[pocketrockets]

Clean install/upgrade feelings aside,

How does Time Machine work. When I plugged in my external HD, it automatically opened, but told me I'd need to delete everything off my external HD. What if I don't want to? I obviously have important files on there that aren't on my computer's HD that I just can't delete.

Time Machine seems very confusing to me and I'm honestly scared to use it (for the reason above). What steps do I need to take? How does it basically work? And what kind of time investment am I looking at?


BTW, my external has 180gb available (out of 250) and I have 50gbs on my computer HD. Thanks for the help!

 

[gr8tfly]

Time Machine requires a HFS+ formatted drive. I'm going to guess your external is FAT32 or NTFS.

If it already is HFS+, it shouldn't need to be erased, as Time Machine puts the backups in a Finder readable folder.

 

[pocketrockets]

How do I find out what format it is? It's a western digital mybook.

WAIT. So now when I plug in my External HD and open Time Machine, it brings me to the Time Machine screen (space theme) and shows in Finder my External HD. But there are no backup files yet. The only thing that exists on my Ex. HD are my previous files that I stored there long ago (the ones I DONT want deleted), the autorun settings, and a new folder called Backups.backupbd (but nothing's in it, except the name of my system). What do I do from here?

Time machine looks cool. But I don't know what to do at this point. How do I back up?

EDIT: BTW, it says in Preferences> Time Machine that Latest Backup: Failed. So it looks like a reformat is required. How do I get my files from the external HD safe, so that I can reformat it. But I don't want it on my computer (takes up way too much space) and I want it only on the external??

EDIT again: Sorry for so many questions, but does using Time Machine completely use up all of the Ex HD space? Does it just overwrite the previous day's data? For example, say I have 50gb on my computer used. Will it store 50gb on the external, and then another 50gb for the next day, and then 50gb for day 3? So already were at 150 gb? How does it work??? Thanks!

 

[gr8tfly]

Use CMD-I to Get Info on the drive (or right-click, or Finder>File>Get Info). It will tell you what format.

AutoRun is a Windows file, so it still seems like your drive is FAT32 (the default for many external drives).

There are some other threads on how Time Machine works (Ars Technica) has a very detailed article on it).

But, to quickly answer your question:

It does incremental backups. So, the first backup of a 50GB drive will be 50GB. If you modify a 1GB file, it will backup just that one file, for a total of 51GB.

If you look through the Backups.backupdb folder, though, you will see folders for each backup - both containing what looks like the complete 50+GB. It isn't, though, because of the method used to write the files (hard links).