[mindajar]

That makes it suck slightly less, but TM can pretty much never be "fast" the way it works now, with the number of files we all have these days. In the best case, if a folder doesn't change, TM can hardlink to the previous backup of that folder. If even one file has changed, it has to copy the changed files and then hardlink every unchanged file in the folder, so TM chokes on any large folder where even a single file changes often. If you watch with `fs_usage -f pathname backupd`, you can see TM take dozens of minutes backing up the Mail/Messages/Calendars folders, or cache folders with ridiculous numbers of files like Slack's. Any folder with thousands or tens of thousands of files is putting TM into its worst-case performance corner.

Personally, I find TM bordering on unusable for backups these days. Maybe I'd feel differently if I still had a desktop Mac, but with a bunch of files on a laptop that moves around and sleeps, having to tether to a USB disk for several hours to do a backup is ridiculous. And network backups are even slower and frequently self-corrupt, especially over WiFi. The glimmer of hope is that APFS replication has some really cool new features in 10.15. It's clearly still very much a work in progress, and some big parts are missing, but the stuff that's released seems to clearly point toward a future where we can do block-based copies of filesystems or even deltas between snapshots. Which is much better for performance on spinning hard disks than the eternal disk seeking and grinding that file-based backup solutions all do.

[bluegreyred]

Not to mention the numerous times where TM casually asks to wipe your backup history because the integrity test didn't pass without errors. Usually this can be fixed with a few commands copied off a blogpost that must be getting thousands of hits every day.

It seems obvious to me that TM was intended to run on a snapshotting filesystem such as ZFS* and when this didn't materialize the engineers tried their best to make it work using the tools available to them. Unfortunately thsoe were sparsebundles and hardlinks. I would hope that TM will get updated to use APFS snapshots sooner rather than later, assuming the feature is proven and stable. iOS makes use of APFS snapshots for rolling back failed updates, so one would assume it is.

* http://dtrace.org/blogs/ahl/2016/06/15/apple_and_zfs/ and https://arstechnica.com/staff/2006/08/4995/

[Razengan]

> a laptop that sleeps

Isn't "Power Nap" (in System Preferences » Energy Saver) supposed to help MacBooks do backup and other maintenance while they're sleeping and on AC?

[m_eiman]

A minor tweak you can do is to exclude specific folders from the stuff to backup, but it'd be nice if the programs creating the caches would mark them as "no need to backup" automatically (which I think is possible?).

Still, I've got three million files on my computer - that's a lot of stuff to walk through. Looking forward to the APFS based replacement!