What data is on the monthly Time Machine Backups?

Discussion in 'macOS' started by HostaDesigner, Mar 4, 2008.

  1. HostaDesigner macrumors newbie

    Jan 26, 2008
    After TM reduces the backups to the monthly backups only, what data is stored on it? Is it all data compiled from the daily backups for the entire month? How does TM treat the monthly backup?

    The reason I ask is, If I add 100 digital pictures per day for a month, are there going to be all 3000 pictures on the monthly backup file after 30 days, or does TM actually delete some of it's backups before the disc is full?

    If it does, I'm struggling to see a huge benefit of it.
  2. aristobrat macrumors G5

    Oct 14, 2005
    I don't think that Time Machine does monthly backups, ... it keeps hourly backups for a day, daily backups for a month, and weekly backups until you drive is full.
  3. mmcxiiad macrumors 6502

    Jul 19, 2002
    time machine does back ups differently then what most people are used to. the first time you back up the computer it does a full backup (with the exception of anything on the do not back up list). from then on it it only backs up new items or changed items.

    this means that if you have a text document and every day add something to it, every day the never one gets backed up. if you change it every hour(or so) it gets backed up every time TM does a back up. Eventually your drive would get full with all of those changes. maybe not from a a text doc, but everything else that is added or changed on your drive. eventually, it is the changed files that start getting dropped. It will never drop the only version of an item though.

    Hopefully this makes sense.
  4. HostaDesigner thread starter macrumors newbie

    Jan 26, 2008
    I could be wrong about the monthly too since I'm away from my home computer right now, but the weekly backup works for this question too. Obviously TM doesn't keep all of the hourly and daily backups. Eventually you can only go "back in time" by 1 week at a time.

    Using the same question, what happens to the daily digital photos that are backed up? 100 photos added per day would lead to 700 images for the week. Would the weekly backup compile all of those photos and contain all 700? Or, does TM simply choose that first or last day in the week and delete the rest? If the rest ARE deleted, that's not much of a backup after 1 week's time. I might as well burn DVDs and archive them.

    TM is new, so I haven't been using it that long. But, a year from now, when my TM is still chugging away, will all of my old photos still be backed up (assuming my hard drive didn't fill up)? If not, why am I even using it is it really doesn't keep a copy of everything?
  5. mmcxiiad macrumors 6502

    Jul 19, 2002
    really time machine doesn't do backups in a day week month concept the way we normally think of it. What it really does is a versioning backup.

    Everything gets backed up once. Changed files get updated. As new versions of a file are backed up. old version of the file are deleted. If a file doesn't get changed there is no need to back it up again.

    so when it talks about hourly, daily & weekly backups - what it is really referring to is the previous versions of a file.

    Imagine you have a 100mb file, A 100GB home directory, and a 200GB drive for backups. Every 2 hours you make a change to that 100mb file. Every time you do TM backs up the whole file all over again. After 10 changes you have 10 version of the file. This is a GB of space devoted to that one file. It is obvious to see that it wouldn't take long for the one file to fill up the backup drive (when you also add in the home directory) since every time it is modified it is backed up.

    To prevent this from happening, TM drops old versions for you so you hard drive is constantly dropping duplicate versions - the oldest removed first.

    But something that is only on there once, never gets removed. it is only the changed files. and with those it is the oldest first.

    So in your example - the pictures are never removed.

    Does that make more sense?
  6. AliensAreFuzzy macrumors 68000


    May 30, 2004
    Madison, WI
    OK, I'll put this simply... The weekly backup will look like what your drive looked like at the end of that week.

    That is to say, if you looked at your drive on Dec 31, then today looked back at the week ending Dec 31 in Time Machine, they would look identical.
  7. HostaDesigner thread starter macrumors newbie

    Jan 26, 2008
    Yeah, that does make more sense. Thanks. It's hard for me to think about a database of modified files in TM organized (somehow) by date over the course of weeks, months, and years, not deleting old unique files, but it DOES delete previous versioned files. Whew.

    Now I'm curious how it handles unique files, where all previous versions are deleted, when the drive gets full. I assume TM halts and declares the disk is full.
  8. AliensAreFuzzy macrumors 68000


    May 30, 2004
    Madison, WI
    That could only occur if your TM drive was smaller than the drive you're backing up from. If that is the case, I'm not sure what would happen
  9. yippy macrumors 68020


    Mar 14, 2004
    Chicago, IL
    Once the disk is full it deletes the oldest backup to make room for the next one. Essentially, once the disk is full, that defines how far back in time you can go from the current date. Example, if you Time Machine drive fills up after 6 months then you will never be able to go back more than 6 months from the current date.
  10. mmcxiiad macrumors 6502

    Jul 19, 2002
    if you are backing up 100gb TM is going to want an extra amount to handle overhead and versioning. say an extra 10GB. I don't know the exact amount but you get the idea. As your drive fills up your TM back up is going to need more as it bare minimum, until it gets to the point where it can't remove any more versioned data and not be able to back up.

    The problem with TM as a backup is all of your eggs are only in 2 places. Your computer's hard drive and this other drive. Should something happen to both (say fire, theft, etc) then what?

    Not to hijack this thread, but I am in the process of trying to figure out how to have a cloned back up of TM to put at a different location.
  11. /V\acpower macrumors 6502a

    Jul 31, 2007
    This whole "deleting older version" must happen only when the disk begin to fill up.

    I mean, I have clearly different versions of the same photoshop file (same name, same directory) in my Time Machine Backup.

    Also, I think you don't directly answer the question.

    Lets make an example.

    We are Monday the 1st. We have a "weekly backup".

    Wednesday, the 3rd, I create a new file. Time Machine does a backup one or two time. Thursday the 4th, I delete the file I created Wednesday. Time Machine does a backup, and on the date "Thursday the 4th", the file is not there in the Backup.

    Then, some time after, Time Machine begin to keep "Weekly backup" of that period. Does a backup called "Monday the 1st", then another one "Monday the 8th". Technically, in backups that are made these two days, the file I created in the middle of the week and then deleted, does not appear in the standard backup. But is Time Machine still keep the file that has been there just for a day in the backup of "Monday the 8th". Because at this time, the backup called by this name is not really what my harddrive was in Monday the 8th. Or in fact the backup is in reality a "Sum of the last week".
  12. mmcxiiad macrumors 6502

    Jul 19, 2002
    Your example doesn't apply to time machine

    a normal simple backup with tape works like this:
    Tape1 - Monday
    Tape2 - Tuesday
    Tape3 - Wednesday
    Tape4 - Thursday
    Tape5 - Friday

    every day you back up to the tape for that day, this overwrites last weeks backup. this is what most people think of when we talk about weekly backups.

    What this doesn't provide is a version backup - which applies to a specific file, not duplicate files of the same thing.

    If I write a document in the morning, and accidently overwrite part of it later that day, then do a backup that night - based on the tape backup all i get is the results at the end of day becouse that is when the backup is done.

    This is VERY different then what Time machine does. Time machine is does a full backup once. Every backup there after is only what has changed. The reason for this is rather then 5 tapes you have 1 drive. so after you write everything it monitors your drive and says "what has changed?" then it backs up those things that have changed. TM backs up every hour based on what has changed.

    So if you open your photoshop file and modify it, we need to back up that file again. If you open it again 3 hours from now and make a change and also save a duplicate copy of it on your drive, now we need to back up the original file again and the new file. This means that each change gives you another version of that file on the backup drive. This is how you go back in time - multiple version of each file.

    Eventually this process of coping every new file and every new version of a file would fill up the drive. So to prevent this from happening older versions of a files are dropped out of backups. Therefore:

    Hourly Backups for the past 24 hours
    Daily backups for the past month
    Weekly Backups until you fill your drive

    What apple is saying here is those modifed copies eventually can't all be backed up, so we start deleting oldest ones first. BUT, there will alway be the most current one. It NEVER deletes the only copy of a file.

    Most importantly, Versioning has to do specifically with a each file individually. A copy of a file is not a new version, it is a new file.

    Does that make more sense?
  13. baleboy macrumors newbie

    May 25, 2009
    does TM ever delete a file??

    mmcxiiad, you are a ledgend my friend

    i find time machines way of describing itself really confusing and you are the first person i have found who has explained this in an easy way.

    i have a 160 gb HD in my macbook, and a 320gb HD back up.its all working well and i have just got my first full message but that seems to be working ok too

    personally i dont care if i can search back through tiny version changes in my drive, i cannot think of a time when i needed an old version of a file from 27th of february all i want to know to sleep at night is 2 things ::

    1..that the most recent version of my files are backedup in TM if i accidentaly deleted it or screwed it up somehow...(yes there are versions but i dont care)

    2. that TM will not delete any unique files EVER..

    i am solid on the first question with the second i am not so sure... here is my example.... my internal drive is full and i need to make space so i am thinking of deleting a bunch of photos. i still want those photos just not on my main drive (i understand this will leave me only one copy for the moment). IF I DELETE FILES ON MY INTERNAL DRIVE WILL TM DELETE THE FILES ON MY TM BACKUP?? or will it just make a copy of every unique file until the drive is full?

    so basically you will get a full message when i have 320GB of unique files even though my main drive is only 160gb

    is that correct?

    sometime i think creating a real time machine would be easier!!!

    look forward to hearing from you...
  14. xraydoc macrumors demi-god


    Oct 9, 2005
    Time Machine will not remove unique files ever, as far as I know, but eventually it will fill the backup drive if/when enough unique files are added to fill the TM drive. I.e., eventually, given enough time and added data, the TM drive will be left with one copy of each and every file, then will simply declare it has no more space to use and stop functioning.

    However, do NOT delete files off your internal drive just to make space and rely on TM to keep a copy around. It's one thing if you do that on a very temporary basis, but remember that if you do, you'll only have that file (photos, in your example) on your TM drive. Should the TM drive explode, you've just lost the only copy. Thus, no backup! You've just put all your photos into one basket (the Time Machine drive, in this case), which is the opposite of what you should do.

    If you need to make room on your main HD, archive the photos to CD or DVD. Sure, let Time Machine back them up, too. But, best safety measure is to set Time Machine and pretend its not there. Don't let the TM drive be the only source of a file.
  15. aristobrat macrumors G5

    Oct 14, 2005
    When that happens, it will prompt the user for permission to start deleting the oldest weekly backups to make room for the newest backups.
  16. xraydoc macrumors demi-god


    Oct 9, 2005
    Yes, but my point was that, eventually, with enough added data, that your Time Machine drive, there will only be enough room for a real time mirror of your primary drive plus a copy of previously deleted files (of which one version will be kept indefinitely).
  17. aristobrat macrumors G5

    Oct 14, 2005
    I've never read where it keeps one version of a file indefinitely.

    I've ready how hourlies rollup in dailys, and how 30 dailys are kept, and after that it only keeps weekly backups, but if the only version of a backed up file is in a weekly backup that the user's given Time Machine permission to cull, that version gets deleted (even if it's the only version). :confused:
  18. baleboy macrumors newbie

    May 25, 2009
    does TM ever delete unique files? what if you delete it from the main drive?

    ok so i was feeling like i was ontop of things for a second there. thanks for all the responses people.

    and then aristobrat comes along and puts questionmarks all over everything again?

    so i guess there is just the debate wether TM ever deletes a unique file even if you delete it from the main drive.

    at that point does it :

    a) follow suit and delete the file

    b) just stop making any more versions and keep the versions it has. and as the drive fills up the oldest versions are deleted until there is just one version which is a full copy of the latest backup of the file. (at this point it is the only copy of tht file left in the world.

    my thinking on this goes as follows: TM is a backup and what is a back up for? to allow you to restore files you have lost screwed up destroyed OR DELETED? .... After pondering this question for a while i am putting my bets on B) BECAUSE WHAT IS THE USE OF A BACKUP DISK IF IT DELETES FILES! time machine cannot decide if a file was deleted accidentally or not. so i am pretty sure that the designers would have thought about this when writing the program (in a perfect world)

    can anyone confirm this ?
  19. aristobrat macrumors G5

    Oct 14, 2005
    The quote below is from the Time Machine help file.

    The attached picture shows the option (which is checked by default) that prevents Time Machine from overwriting your old data without your permission.

    Attached Files:

    • TM.png
      File size:
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  20. aidricksdad macrumors regular


    Dec 29, 2008
    Round Rock
    can i go into time machine and delete big files to save room...like lets say i out a 8gb file on my mac, then decided to put it on my external drive instead but tm has already backed it up...can i go and delete it myself and save the 8gb or will i slowly fade away unless my parents kiss?
  21. aristobrat macrumors G5

    Oct 14, 2005
    If you're in Time Machine and highlight a file, you can hit the delete key to remove that one version, or you can hit the icon of the gears and then there's an option to delete all versions of that file.
  22. baleboy macrumors newbie

    May 25, 2009
    "Also, as your backup disk fills up, Time Machine deletes older backups to make room for new ones. You may be able to use Time Machine for a long time before running out of space on your backup disk."

    so maybe i am totally stupid but when TM talks about past backups does it mean past versions of files that have newer versions or ust old files.

    why is this not spelled out clearly anywhere?
  23. aristobrat macrumors G5

    Oct 14, 2005
    AFAIK, it goes back to the oldest weekly backup and deletes that. So any version of a file that was backed up during that week is gone.

    I have no idea why Apple doesn't spell it out more clearly. And my guess is that most people haven't had their Time Machine drive fill up yet, so there's not a lot of people with first-hand experience.

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