Just going to say out of the chute that Time Machine has pretty much been flawless for me since I got a Mac. It’s saved my bacon more than once. Which is why I was surprised when trying to do the first backup of my work Mac that it wasn’t even finishing after days.

Days. With a Samsung T5 external SSD drive running on a MacBook Pro with an M1 Pro chip. I even set it to ignore stuff like the Applications folder, my Parallels VM folder, etc. Nothing made a difference. In situations like this I often turn to Howard Oakley over at The Eclectic Light Company.

Howard has a diagnostic tool for Time Machine called T2M2 but it didn’t help me. More searching on his website brought up How to make Time Machine backups faster. I had already tried everything he mentioned there except for removing I/O throttling.

Funny enough this is the method most people have mentioned since about 2016 (and of course I had never heard of it in the ensuing 7 years). The command sudo sysctl debug.lowpri_throttle_enabled=0 turns off the normal low priority that Time Machine has on the system (found out later that App Tamer also has this as an available setting). To say that it made a huge difference was an understatement. My backup completed in a couple of minutes once I flipped that setting to disabled. I then removed everything I had added to the ignore list in Time Machine’s settings which added about another 10 minutes and I was done.

There are two things to note with this command though: it resets upon reboot and it’s a global setting, so now any other process that was set to a low priority is now potentially taking more resources.

I’m still trying to figure out what was causing it to be so slow. None of my other Macs have this issue but none of them have all of the corporate crap installed on them either. I thought I had disabled all of that too but nothing made a difference until I changed that flag. It’s worth a try if you’re having the same issue.