What the flarg is Time Machine backing up at 1, 2, 3, 4, 5 etc in the morning??

Discussion in 'macOS' started by RoboCop001, Dec 12, 2007.

  1. RoboCop001 macrumors 65816

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    #1
    So I left my MacBook Pro on last night, because I was probably not downloading episodes of some sort of television show because I missed them or some equally lame excuse, but in fact left it on for some other reason, and when I went to check Time Machine, it listed backups for the whole night on an hourly basis.

    Well, it wasn't downloading to my internal drive. Nothing changed on the drive. The only thing that was open was Transmission. In fact, it was downloading to my Time Machine disc, because I use it for storage and backups.

    So what the flarg is happening here? Even if it's just a few MBs that it's backing up, I'd like to save space. So if anyone knows of any good ideas of what to exclude, that would be fantastic.

    Incidentally, a flarg is a vicious lava beast that lives in the depths of evil caves... in lava.
     
  2. jsgreen macrumors 6502

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    #2
    TM backs up incrementally every hour - if your files haven't changed there should be almost no drive space used (what looks like files are aliases if unchanged from the previous hour's backup).

    These roll off daily/weekly/monthly I believe.
     
  3. CashGap macrumors 6502

    CashGap

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    #3
    Yep, this had me stumped at first.

    Time machine "creates" a complete backup set every hour. HOWEVER, that complete backup set can consist entirely of links to files that are present in other backups.

    The attached image is from my Time Machine drive backup set. I left work last night at about 5:30pm. I returned this morning at about 6:30am. So the 6:05pm backup probably consumed disk space, consisting of the files I'd modified since the last backup. It also has a link to every other file on my drive that had not changed, but those links take no space.

    The 7:05pm through 6:06am backups occurred but took no space (and probably took next to no time to complete).

    The 7:05am backup space used would be the size of whatever files I modifed after I arrived this morning.

    I hope that makes sense. It's actually a robust model. When you are restoring, you don't need to remember "Let's see... did I work late that night?". Just roll back to the point that your needed files exist and go from there.
     

    Attached Files:

  4. saltyzoo macrumors 65816

    saltyzoo

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    #4
    log files, email if email was running (you said nothing was running, but....) there's always something running. And a lot of it writes to log files. They'll likely be so small as to not worry about.
     
  5. RoboCop001 thread starter macrumors 65816

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    #5
    So they're aliases, but they don't show up as aliases?
     
  6. Phil A. Moderator

    Phil A.

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    #6
    I think they're actually hard links rather than soft links (aliases). See here for a bit of background on hard and soft links in Unix
     
  7. CashGap macrumors 6502

    CashGap

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    #7
    Originally Posted by RoboCop001
    So they're aliases, but they don't show up as aliases?

    Yep. Very elegant and simple, actually. Think about this for a moment... the 6:05am backup on my Time Machine disk took up 0 space. But if I restore it, I get everything. And I can delete every single backup from the disk EXCEPT the 6:05am backup and still have a complete backup set. Nicely done.
     
  8. Eraserhead macrumors G4

    Eraserhead

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    #8
  9. walnuts macrumors 6502

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    #9
    I don't know if this is so useful. My iMac is close to my bed, so I can confirm that my Mac wakes up every hour, the external spins away for a few moments, etc. Isn't that wasteful of both backups and power? I'd rather have a backup of the last 24 active hours. Also, how much power does it use to wake from sleep every hour? It would seem that it would almost be more power than leaving the thing running all night long. I imagine that if I had a laptop that that would be really annoying.
     
  10. CashGap macrumors 6502

    CashGap

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    #10
    Power is so cheap it's practically free in real terms, and no backup space is used so that's not an issue at all. Eh, for a laptop, I guess it could be in sleep mode with no AC power yet still have the external drive mounted, but that's probably not common. Usually if the external drive is connected the laptop is running on mains.
     
  11. notjustjay macrumors 603

    notjustjay

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    #11
    Is there a way to specify hours of operation for Time Machine?

    It'd be nice if you could tell it not to make backups between 1:00am and 9:00am if you're always asleep then and your files never change.
     
  12. Mindflux macrumors 68000

    Mindflux

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    #12
    If the file hasn't changed then all it's doing is providing a hard link to a previous backup (last time it was changed).

    The backups in which are almost 100% hardlinks have to be VERY VERY tiny. Why bother worrying?
     
  13. apfhex macrumors 68030

    apfhex

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    #13
    Time Machine doesn't wake the computer from sleep, or at least it shouldn't b able to. It doesn't wake mine. It will wake the HDD from sleep, only if you left the computer on.

    If someone's worried about TM taking up a few extra MB with hourly backups, well I think that's silly. You should probably be using a backup drive big enough that space doesn't turn into an issue immediately anyway.
     
  14. notjustjay macrumors 603

    notjustjay

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    #14
    I was more concerned about having it wake your Mac from sleep and spin the drive up and down, but the post below yours suggests that this does NOT generally happen, so perhaps it's a moot point.
     
  15. walnuts macrumors 6502

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    #15
    Why shouldn't it be able to wake it from sleep?

    Also, I should clarify- the monitor doesn't turn on, but I do (think) it wakes from sleep. Normally, when I go to the computer in the morning, I can tell that it is waking from sleep (I can hear the hard drive and cd drive start to spin, the wifi takes a moment to kick in, etc.) However, now that time machine is active, occasionally I will come to it and find it responds immediately (as if only the monitor was asleep, not the mac). I presume that its because it woke up to do a backup.
     
  16. THX1139 macrumors 68000

    THX1139

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    #16
    Why does the average person need a backup every hour? It's one of the lamest things about Time Machine. There should be a setting in preferences that allows you to designate times for backups. I looked for some 3rd party solutions and hacks but so far nothing has worked as expected. I even setup a script to activate a backup via an alarm in iCal, but that didn't work like I hoped. Now I just turn off Time Machine and then manually run a backup when I log off at night or whenever I finish a major session of work. You'd think with all the time functions built into this modern computer that you would be able to control when a backup runs.
     
  17. brop52 macrumors 68000

    brop52

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    #17
    Shut off the external HD and you control how often you want to backup by turning it on. Simple solution.
     
  18. Makosuke macrumors 603

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    #18
    I'm going to agree with the other poster here--while it's technically possible for a program to wake the machine to do a backup (my pre-Time Machine backup software did this), Time Machine doesn't. At least, it certainly doesn't on my G5 tower. It will do a backup promptly upon waking if it missed the last hour, but the machine stays sound asleep for days at a time.

    And this is with an internal TM disk, so it's always available.

    Sure it's not something else waking your computer from sleep?
     
  19. SidBoggle macrumors regular

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    #19
    I can also confirm that time machine does NOT wake my macbook up every hour for backup. It simply waits for the next scheduled backup time after I have woken the macbook.
     
  20. CashGap macrumors 6502

    CashGap

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    #20

    The hourly backup has ZERO meaningful cost (time, space, energy, etc.) and at least marginal value.

    With Time Machine, every user gets a good backup. If they add tons of configuration options... users who understand the configuration options get a good backup. Users who don't understand the configuration options get... something, maybe a good backup, maybe an "aw shucks I guess I shouldn't have tweaked that setting" experience.
     

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