Sorry, but that's basically all incorrect.
TM backs up everything... There is no documents folder (only) to it, unless you go into the TM preferences and start excluding items from the backups.
It does not save anything that was "saved" since the previous session, it saves everything that "changed" since the last session.
There is no being "modified and saved again" about it.
If you saved a file 2 years ago and started TM backups, never open that file again, don't delete that file from your internal drive and have kept TM backups for the past 2 years, that file that was saved 2 years ago will be in the "current" TM backup - even if the external drive has begun deleting old files. It only deletes files and versions of files that are not now currently on your internal drive. It does not delete anything from the backup that currently exists on your internal drive.
Eventually you would reach a point in the future where the oldest backup doesn't have the file you want but for most people that takes quite a while.
That's what I was getting at in my scenario. I still don't understand exactly what TM does, but apparently there is the potential of losing a file from the backups without you knowing it. Such a file would be one you want to keep, but don't have to change.
Oh, absolutely. My Documents folder is also on a flash drive AND online (IDrive). Triple redundancy should be enough. TM is really only for other stuff for me. Although it backs up my Documents folder as well, it would be my last resort if the hard drive, flash drive and IDrive fail me at the same time.Time Machine gives you a warning when it starts deleting the oldest backups. For the scenario you propose where there is a file that isn't being modified your best bet would be to archive the file on something like a DVD before it is deleted from the Time Machine backup.
Since this conflicts with other information provided in this thread, and I've come to trust the advice of both purveyors of said information, and I don't really know myself, I'll continue with the above redundant copies to stay on the safe side. It really doesn't matter to me how TM works on a practical level. I'm just curious.There is no potential of TM deleting a file from the backup that you did not already delete from the internal drive.
time machine is not for storing files you want to keep but don't want on your internal drive any longer. For that, you get 2 more drives - one for data storage of things you want to keep but don't want taking up space on your boot drive and the second to backup that storage drive.
Since this conflicts with other information provided in this thread, and I've come to trust the advice of both purveyors of said information, and I don't really know myself, I'll continue with the above redundant copies to stay on the safe side. It really doesn't matter to me how TM works on a practical level. I'm just curious.
If I delete files on my MacPro, what happens to those files on Time Machine?