Is there a way to restrict Time Machine backups to a given size?

Question

I'm using a Time Capsule to do Backups, I've been doing this for a while now. The problem is that the backup begins small and with time it becomes huge. So restricting its size would make Time Machine use it's own space saving operations (I guess).

My idea would be to change the sparsebundle's size limit to a size much smaller than the hard drive's size. Since the sparsebundle is where the backups are done it should restrict available space and cause pruning when that limit is reached.

Would resizing the Sparsebundle cause any problem for the reliability or function of Time Machine?

Answer 1

You could try using the Disk Utility to make a partition of a given size, and then having Time Machine backup to that partition.

Answer 2

From https://dongknows.com/this-trick-will-keep-time-machine-backup-storage-use-under-control/:

• Determine the storage limit: Generally, 150% of the capacity of the Mac’s internal drive is a generous limit. Now convert that number in megabytes (MB).
• sudo defaults write /Library/Preferences/com.apple.TimeMachine MaxSize CALCULATEDMAXSIZE

Once the backup file exceeds limited storage, old data will be deleted, so make sure you have a good choice of the limitation.

Note: according to the article, this only works up to Sierra (macOS 10.12) or earlier.

Answer 3

There aren’s viable ways to do this. Moreover, other controls are equally effective and less hassle/risk to implement. By watching what’s actually changing week to week and skipping less needed items if you can’t afford a storage to have a time interval of data you prefer (18 months of snapshots, for example). Also, the command line tools for deleting a specific file or folder lets you surgically reclaim space and manage things other than forcing a brute force prune.

• get a physical drive or two
• avoid network backups as your only destination, especially if they are RAID or don’t have a backup.

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I much prefer to let the backup grow to take all available space if needed and just look at things when I set it up - maybe once every three days for a week or two then once a week or once a month till you are comfortable about the growth.

When I find there's something taking a lot of space and I don't want it backed up - say the iPhotos library on a portable when the master library is in iCloud and synced to a Mac mini at home - I don't need to back up the optimized version on the MacBook. Set Time Machine to exclude the library and then I go into Time Machine interface and select that library and use the gear control to delete all backups of that library file. (folder / package to be correct in the case of Photos).

This way, I have just the files I need backed up and no hassle guessing sizes before hand and restricting things. I always can get notified when the oldest backup gets cleaned and can see the space grow.

Lastly - I use a very slick tool that could help you analyze and alert you to large backup intervals.

• http://www.soma-zone.com/BackupLoupe/

You can do much of what it does manually with tmutil compare but I love the ease and graphs it provides.