Q: Yosemite and Time Machine

Not something I've ever come across, but suggest having a read through this https://developer.apple.com/library/mac/documentation/Darwin/Reference/Manpages/ man8/tmutil.8.html

especially the text under associate disk and inheritdisk.

Note though its the 'Mavericks' version; can't see that Apple updated them anywhere. The pages on Unix.com seem identical at first glance

The 10.10.1 release  did NOT fix this for me

My backups have been suffering from the symptoms described in this thread recently but the thread itself has gone quiet.

Did a solution appear (unlikely). Have people found http://timesoftware.free.fr/timemachineeditor/ useful when looking for workarounds?

I was having serious problems using Time Machine when I updated to Yosemite for about 6 months. Then an update, that didn't even list Time Machine as a repair, fixed it. I am guessing that most people with TM problems, received this update, and it repaired there problem as well, because discussion seemed to stop after it was sent out. Still if an update fixed it, then it must have been, not as rare a problem, as apple said it was. Again although this update, didn't have 'anything,' listed about time machine, it fixed the TM problem I was facing. The major thing that that Yosemite update actually mentioned was WiFi. How this update mysteriously fixed my TM problem, is completely beyond me.  Perhaps the update was never sent to you. I really hate to offer this as a solution, but perhaps you could take it to an apple store. They should probably know what the problem is. When they fix it, demand that they completely explain to you why your machine had problems using Time Machine.

I've never used Time Machine editor, but thank you for pointing out this application too me. My backup drive only has about a 1 TB of room, and quickly gets full. That app looks handy, but I don't see how it could fix a Time Machine problem, except by possibly creating more space in your back up drive. Unfortunately I don't think that not having space is your problem. TM should just automatically just ask you, if you would like to overwrite your old backups, hen it gets full. I will look more into its safety of use, but cutting down some on the frequency of backups, might come in handy. This would increase to amount of time my backups can go back to, potentially by a lot.

I really hope that someone here, can still offer you some assistance ...

Greenmind, thanks for coming back to me. I am up-to-date with my patches but I think my specific case is not quite the same as the one in this thread. The problem I have is when I use a second disk, which I plug in locally every weekend to make a second backup. During the week I backup over my LAN to a QNAP. Recently, after the weekend backup to the local disk is done, and I turn it off, Time Machine asks me to create a new full backup on the QNAP.

I've tried repairing the sparsebundle with disk util and fsck does not report any issues. Maybe I have hit a filesystem limit as some threads suggest. I think I'll just have to swallow another full backup and try to work out a process that lets me use two disks.

Very annoying of course because not only did it used to work fine, it has also destroyed my backup history. Another nail in the coffin of Apple as far as I am concerned; the operating system has turned into bloatware, just so complex. I hate to say it but Centos 7 is looking like a very nice desktop solution...

I am having the same problem with the mounting and dismounting external drive which is backed also to the same TM drive, i am on 10.10.5 and it was there since the beginning of 10.10.

Any solutions as of today?

IMHO its still broken.

If you have TM backing up an external drive then you basically have two options

1. Always keep the drive mounted when TM runs, or

2. Keep the free space on the TM disk greater than the used space on the (dismounted) external drive

I'd express an opinion but then the post would be deleted.

Do you mean, I turn off TM every time I finish backing up, and whenever I want to back up data I mount the external HDD to be backed up before turning TM on again?

Does this mean, every time TM run without the external HDD mounted,, I will go into the same issue?

Thanks in advance for your reply.

Yes, every time TM runs without the external disk mounted you potentially have a problem.

If TM runs when the disk is dismounted, then next time the disk is mounted and TM runs - TM uses the 'Used' space on the drive in its calculations.

So,

A. if you keep the external drive mounted - you never have this problem, or

B. You have a problem if you dismount the disk, remount it and the free space on the TM drive is less than:

1. the used space on the external disk, plus
2. any deltas on other drives. plus
3. the padding TM adds

Prior to Yosemite, in case B1, TM would scan the external disk and calculate the true difference between what was on the external disk and the previous backup for that disk so this problem didn't arise.

Your choices are:

1. Turn TM off before you dismount the disk and turn it back on after you have remounted it, not good because it means other disks are not being backed up, or

2. Keep the external disk mounted all the time, not good because it should not be necessary (and was't in Mavericks) or

3. Keep lots of free space on the TM disk

Thanks so much for the detailed explanation,

I will personally go with Choice 1 as I am using a MacBook Pro 15" mid 2014, and with mobility, I can't have the 2 external drives (work and Photography) attached all the time, I just placed an order for the new 12 TB WD my book Duo, as my total Backups went beyond 3 TB, so choice 3 will take effect once I get it in RAID1 6TB storage.

Sure I will mount them later (with choice 3) one by one (TM backups in between), other wise TM will want their combined space which will exceed my limits.

I believe your posts helped me so much understanding choices and how to overcome that bad implementation done by Apple in 10.10, hope El Capitan solve this soon.

Thanks again,