Although they can only grow in size, and mustn’t be left lying around, snapshots can be very useful, provided you manage them carefully, as described here.
Time Machine
How do you locate part of a document that you removed or changed greatly, and copy that content into the version you’re currently editing? What to do when it’s too much for Undo.
Caching to disk improves performance, but cached data are optional and may be purged when additional free space is needed. This explains how that’s performed by the deleted service.
Major improvements in its plots make this new utility even better for tracking changes in used space, and so forecasting how long backup storage will take to fill.
Further tests on two volumes with over 90 GB purgeable space. One took almost 30 minuted to become available, the other never got there at all. The log reveals who was responsible.
Snapshots made by Time Machine and tmutil should be purgeable, although sometimes they won’t purge, and aren’t shown reliably as purgeable space. An exploration of bugs and missing documentation.
If you leave your Mac running overnight, but not sleeping, what does it do? Does it perform maintenance tasks that it would otherwise have to do during the day?
Nine days of measurements of used space on a Time Machine backup storage drive. What does DeltaFree predict for its lifetime? How does used space change in containers in the internal SSD?
To work out how long you’ll be able to use your present backup storage, you need to know how much space is free now, and the rate at which free space is being used by further backups. This app can forecast that, and more.
Does your backup storage really need to be twice the capacity of your Mac’s internal SSD? If you’re already backing it up you can estimate the size required more accurately, as given here.
The Eclectic Light Company 