Time Machine deleted itself entirely!!

Discussion in 'macOS' started by all-in-my-head, Sep 7, 2010.

  1. all-in-my-head macrumors member

    Joined:
    Oct 25, 2003
    Location:
    UK
    #1
    This is a major Time Machine flaw! :mad:

    I know time machine deletes old backups when full, but in the last hour my Time Machine (without warning) deleted its entire history of backups to make space for one stupid hourly backup. So i've gone from 6 weeks of backup info to one hours worth!

    Only after this did it tell me (the following hour I presume) that there was not enough space to perform a backup. So my reckoning if your backup gets anywhere near half the size of the backup drive you loose the lot.

    In my case I was trying to sort some permissions errors and working on new network accounts so had to duplicate some files to fix permissions and temporarily doubled up on a lot of data.

    Amongst all that I needed a fresh copy of some system files and went to TM to grab them to discover everything gone.

    I had two HD's (250GB and mostly empty 500GB) backing up to a 1TB drive. I guess all this has happened 'by design' to make it consumer friendly(!), but the lack of options in TM is really to its own downfall.

    (Marks my second major disappointment of Apple software - after lame iOS multitasking interface/concept)
     
  2. MacForScience macrumors 6502

    MacForScience

    Joined:
    Sep 7, 2010
    Location:
    USA
    #2
    Your issue:
    Future reference if you are going to double your data temporarily with such a small backup drive unmount your time machine volume. This is what we call operator error combined with imperfect software. I learned this the hard way just like you.

    Cheers
     
  3. diazj3 macrumors 6502a

    Joined:
    Jan 19, 2008
    #3
    well, no backup method or software is flawless... but a general principle is to keep your backups safe, specially when fiddling with the system or doing non-standard system maintenence. If you decide to temporarly duplicate a big ammount of files in your drive, TM will try to back them up too (unless they're in the "ignore" list"), and if space runs out, it'll delete previous backups. I'm not sure TM is at fault here.

    For example, I had a similar experience when installing a hard drive in my MP that had a lot of data: when TM registered it, it started backing up the new drive too and deleted older TM backups to make room for the new information. It was until I noticed the TM backup was taking too long that I realized the problem, but it was too late and the previous backups were gone. The lesson I learned is to change the TM settings to "manual" and put the new drives or duplicated directories in the ignore list. I really can't blame TM for this, since it's programmed to do just that. I've kept TM in manual mode since.
     
  4. MacForScience macrumors 6502

    MacForScience

    Joined:
    Sep 7, 2010
    Location:
    USA
    #4
    Ok, thats why you eject your Time Machine volume before you start your modifications perform them then re-mount the time machine volume. You completely avoid the issue and you can duplicate as much as you want. You also don't have to bother with the ignore list.
     
  5. diazj3 macrumors 6502a

    Joined:
    Jan 19, 2008
    #5
    that's another way to do it... but the moment you restart or log-in, TM will detect changes and start the delete/backup process. To be 100% safe, you'd have to turn TM off, and/or include the directories in the ignore list. Plus, depending on your setup (having the TM drive externally or internally), the best thing to do is turn TM off AND disconnect/extract the drive while performing such tasks. If the tasks you perform modify data greater than the available space in the backup drive, or create/migrate to a new user name, look for another TM space (e.g. another TM drive or partition, and access it through a TM utility such as Back-in-Time).

    cheers!
     
  6. all-in-my-head thread starter macrumors member

    Joined:
    Oct 25, 2003
    Location:
    UK
    #6
    Changing Permissions was the real problem?

    It's nice to know I'm not the only person this has happened to and while I fully get Time Machine is working as designed and is not failing as such, I think it makes for a poor design - maybe a few more settings would hugely improve it.

    However, on going over everything I did again I've discovered that while having an ignore list would have helped for file duplicates, what actually caused this to go the extreme of deleting everything was changing permissions.

    Essentially after following Apples KB article on changing the user shortname (I know a bad idea and a whole other story!), and then correcting the bits Apple process didn't do, I ended up changing permissions on every user owned file on both drives. This basically flagged everything as been changed and needing a 'fresh' backup.

    The problem is therefore more down to TM not creating a database of changes (like iPhoto editing does), but just duplicating the whole file. So a small (in data terms) change of permission ends up in a huge backup.

    So it would seem none of the great suggestions, which I'll be following in the future, would have helped in this case.

    Does anyone more more than this - how does TM deal with backups?
    I've got a Genius appt. soon I'll ask them there too.
     
  7. diazj3 macrumors 6502a

    Joined:
    Jan 19, 2008
    #7
    The thing about Time Machine is that it's designed to help the average user that has a practical and basic understanding about backups and computers, and wants a hassle-free automatic backup to rescue a recently deleted work file. In this respect, TM is perfect, as it also solves user's primary backup conundrums: complication, procrastination and forgetfulness.... but it's not a comprehensive backup solution by any means.

    I think TM assumes such average user will not fiddle around with system files, permissions, user accounts, etc (at least, not without the help of an Apple "genius" or other guidance).... it's a fool-proof-basic backup system. Its Aquiles heel - as every backup system has one - is the fact that it will automatically delete whichever backed-up information when newer information surpasses the available space in the TM drive, as it assumes newer data is more important than older data.

    If you are beyond that user level of knowledge - e.g. a user that fiddles with the system and that is not bound to backup traditional user files and apps - then TM is no longer the only backup solution for you, and you should combine it with another backup method, such as system cloning (using CCC or SuperDuper), and know better before performing such file duplication (turning TM off / disconnecting the drive). I'd recommend a RAID mirror, but it would bring you the same problem...

    Keep in mind that a) any backup system you choose will always be limited by the available space you have to store your backups, regardless of any "database of changes" it creates. And b) when it comes to backup apps, there's always a trade-off between automated convenience and customizable safety.

    But hey, feel free to nag about it.... IMO it's each users responsibility to observe TM's basic behavior during whatever off-limits maintenance performance. Don't feel bad about it - it has happened to the best of the best. Live and learn my friend.... live and learn :p

    Cheers!
     
  8. maflynn Moderator

    maflynn

    Staff Member

    Joined:
    May 3, 2009
    Location:
    Boston
    #8
    One of the biggest issues Time Machine has is that if there is not enough room to back up your data, i.e., it sees more changes then what the storage will allow. It will start deleting older backups. The problem arises when it needs to remove all just to back up the current set.

    I use two backup methods, Time Machine for those times when I deleted a document I need to retrieve or changed a file I should not have. This is great at that this task.

    I also use Carbon Copy Cloner on a separate hard drive so if the system becomes messed up, I have a fast efficient method to recover my system. TM is wicked slow when doing a full system restore, so CCC is my preferred method.
     

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