Time machine is confusing

I have used time machine backup before, but I'm confused by what it really is doing. it says it will copy the whole disc at first, which can take a n hour or more, i understand, and then it says every hour when it is active it backs up tthe current state, and does so by copying only the files that have been added since. the last backup. Ok that makes sense. What about if i delete some fiiles ? Are they deleted from the current back up some how? How can it save deleted files information? does it save a record of the folder contents n some kind of list snf then not include the deleted ones, but that is not what appears on the external drive. It appears to have many copies of the whole kit and kaboodle, They aren't aliases of the files or at least they don't register as aliases. But that must be what itis . The previous versions of the backups from every hour back through the 1 hour intervals appear to be the whole backup. i had a smaller ext hd once for this and when Timemachine reached the capacity of the disc, without any warning at all, it automatically erased the oldest backup! so I shut it down instantly. here's the issue if you have not guessed. I deleted files to make room on my computer's internal drive, routinely, because i was secure iin the knowledge that Time machine had already backed up those files adn i could get them back any time. Then Time machine began to erase older versions of the hard drive , effectively losing my files i deleted specifiacally because they were backed up! suck!.In this case time machine did the exac opposite of what it is for.

Nothing at all confusing about Time Machine. Just let it do its thing and make sure you have a large enough external drive to hold however far back in time you wish to go. But keep this in mind... you'll reach a certain point in saving backups where they'll become useless and outmoded by updates to OS X. I keep one year and even that is probably too long.

old tinkerer said:

What about if i delete some fiiles ? Are they deleted from the current back up some how?

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Yes...if those files were deleted...then that is a change. The next time Time Machine (TM) does a backup...those files won't be there (you deleted them). But if you go back a couple backups...those files will still be there (until the older TM backups are overwritten).

old tinkerer said:

How can it save deleted files information?

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It doesn't...as I mentioned above.

old tinkerer said:

It appears to have many copies of the whole kit and kaboodle, They aren't aliases of the files or at least they don't register as aliases. But that must be what itis . The previous versions of the backups from every hour back through the 1 hour intervals appear to be the whole backup.

Click to expand...

This is the way it works. TM makes backups every hour of only what changed fro the previous hour backup.

old tinkerer said:

i had a smaller ext hd once for this and when Timemachine reached the capacity of the disc, without any warning at all, it automatically erased the oldest backup!

Click to expand...

This is exactly how TM works. It keeps making hourly backups until the drive is full. Then it starts overwriting the oldest backups. TM uses the FIFO accounting method (First In...First Out).

old tinkerer said:

here's the issue if you have not guessed. I deleted files to make room on my computer's internal drive, routinely, because i was secure iin the knowledge that Time machine had already backed up those files adn i could get them back any time. Then Time machine began to erase older versions of the hard drive , effectively losing my files i deleted specifiacally because they were backed up! suck!.In this case time machine did the exac opposite of what it is for.

Click to expand...

If those files are important...then either:

- Don't delete them from the hard drive in the first place. You can't treat Time machine like it's some sort of endless/bottomless storage space. You can't just delete files as you feel to make space when using TM. Time Machine with the hourly backups saves a snapshot or mirror image of what's on your HD. If you delete something...then it should only be deleted if you no longer want or need it. Not to create space. Otherwise those files will be permenently deleted when TM overwrites the oldest backups exactly as you described.

Time Machine makes backups that mirror your HD at the time of the backup. Erase/delete some files...and yes...they will eventually be lost. So don't delete them if they are important.

- back them up onto a USB stick, on the "Cloud", or on a 2nd external hard drive via the "drag & drop" method (just copy it to an external source manually). This is the way you create space on an internal HD that is getting full. You "off-load" files that are important onto an external storage device.

- Nick

As chscag mentioned. The larger the external HD used for TM backups...the longer files that may have been deleted will still be there. But even with a very large external HD...those deleted files will eventually be overwritten when the HD gets full.

When using TM only delete files if you no longer need or want them. Otherwise eventually they WILL be lost.

- Nick

I agree with the above comments. The OP has a fundamental misunderstanding of how backups work. To clear space on the boot drive but not lose the file, you'll want to put that material on a separate partition or alternate drive, the way a LOT of people do with their media libraries (photos/music/video), and then (of course) back up the media libraries ...

This is exactly what I do. I have now two 3TB drives and a portable 1TB drive. The smaller one is my Time Machine backup of my boot drive (which is also 1TB but only half full), the first 3TB external is the media library, the second 3TB is a clone of the media library ... and I have a (not updated lately) 1TB clone of the boot drive for troubleshooting purposes.

The general recommendation is that the TM volume should be twice the size of the drive(s) it is backing up. Mine is and I have backups almost a year old on it with the backup drive only 2/3rds full. You do have to be mindful that the oldest backup will be deleted first, so as Nick (pigoo3) says, don't put things you want to keep forever in TM. Put them in some other storage, preferably a longer term storage, instead.