• Apple OS X

  Why does Time Machine tell me my 1TB backup disk is too full, when it’s not?

  Posted by Ted Coakley on October 29, 2018 at 10:05 pm

  I’m running OS10.9.5
  Backup drive size: 1TB
  Internal drive (being backed up) used drive size: 796GB

  Specifically, the Time Machine Failed message says:
  “Time Machine couldn’t complete the backup to “Time Machine SSD & extra HDD space backup.
  The backup disk needs 180.31 GB for the backup but only 92.74 GB are available. Select a larger backup disk or make the backup smaller by excluding files.”

  There’s 2 things wrong with this:
  First, my 1TB backup drive is 25% bigger than the 796GB size of consumed space on the drive it is backing up, so there actually IS plenty of space on backup drive for a full backup.
  Second, even if backup drive is totally full, it shouldn’t matter, because Time Machine does Integral backups, wherein, if the Time Machine backup drive gets full, it is supposed to just delete old backups on itself, until there is room for most recent backups.

  SO, with that in mind, as long as the backup drive (not available space, but the drive itself) that is getting backed up TO is not smaller than the used space on the drive being backed up from, Time Machine should not be telling me that the backup drive is too full and that I should exclude files to be backed up, but rather Time Machine should just be deleting some (or all, if necessary) old backups, until room for latest backup.

  Anyone know how to fix this?

  Thanks,
  Ted

  John Rofrano replied 7 years, 6 months ago 2 Members · 1 Reply
• 1 Reply

• 

  John Rofrano

  November 2, 2018 at 1:36 am

  Just a guess but perhaps it can’t free up enough space and also hold the next incremental backup. Do the math… 796GB + the backup disk needs 180.31 GB for the next backup = 976.31. I’m guessing that the 1TB drive isn’t exactly 1TB (it’s a littler less after the drive is formatted) so your complete backup + incremental might still exceed the drives capacity.

  If you don’t care about rolling back, I would format the Time Machine drive and just do a full backup again. You really should get a 2TB drive too backup 796GB of data and still have enough room for a few incremental. The Machine normally backs up every hour and I doubt you changed 180.31GB of data in an hour so it sounds like you are not doing continuous backups anyway. Alternately, don’t wait so long between backups next time.

  ~jr

  http://www.johnrofrano.com
  http://www.vasstsoftware.com

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