Painfully slow Time Machine backup.


Jan 10, 2012
Damn. I had no idea. Well, as I said -- WD is big enough to make drives with custom interfaces.

I always buy bare drives and empty enclosures, so I've never noticed anything like this.

Sorry not to have been able to offer useful advice.
"I always buy bare drives and empty enclosures, so I've never noticed anything like this. " - This is very good advice and I usually do this, except for this time. Lesson learned. Haha :) Thanks!
Mine took over 7 hours once
Yeah I'm noticing, unless you do the renice priority settings, any mouse movement or usage on the Mac results in Time Machine backup going to 0 (mine can show 4 hours for 200MB) - until I stop moving the mouse, let it sit for a few mins, then it backs it up in less than 10 mins. I'm starting to think the drive also has throughput problems too (in my case).

That said, It would be nice for Time Machine to have a : "Hey, this is a MacBook that doesn't sit idle for long periods of time, backup ASAP, full resources" option. :p

I'm keeping Time Machine for now, but really liking CCC's backup options.
Last edited:


macrumors 68000
Feb 29, 2008
Los Angeles
Before I upgraded to Mojave this evening, I first attempted to backup my Mac using Time Machine which hadn’t been done for about 2 weeks. The backup size was 14GB, and the backup was painfully slow as others have commented here. The estimated time was 20 hours.

I followed the instructions on the article linked below, which made the process speed up significantly. Not as fast as it used to be, I estimate it backed up 14GB in about 25-30 minutes.
  • Like
Reactions: BigMcGuire


macrumors newbie
Nov 19, 2017
Houston Texas
I have installed Catalina on my 2014 iMac that has a 1tb ssd and a 256gb flash usb (3.0) drive for backups. I opened and started TM to do the initial backup. I have 67gb of data I want backed up. After 30 hours with iMac running it has backed up 1gb so it says “calculating remains time” with no estimate. At this rate it will only take 67 more days to do the initial backup. I tried all the restarts, erased the .inprogress file and started over, four times, with no improvement. I can use Finder or “save as“ much easier than TM, so WTF? Is this what I have to endure?

Brian Josephson

macrumors newbie
Feb 16, 2020
Another complaint about Time Machine backups. I have an encrypted 4TB drive as my TM backup - direct USB C to USB 3.x cable (to my WD 4TB drive).

Backups are consistently getting slower and slower. It takes hours to do 300-800MB backups. I have a 3.6GB backup, after the last Mac OS update that is estimating 18 hours. It goes down to about 9 hours if I don't touch the mouse and let the laptop "idle" - but this is insane.

I've noticed it getting slower and slower. I know it isn't the drive because I can use Arq backup and it'll write 17mb/sec to the drive. I can run apps off the drive and do iTunes backups to the drive, no problem.

These time machine backups are just getting slower and slower. It's at 97% encryption too (which has taken weeks to get to).

So, I just found out about 2 Mac commands that seem to have made a pretty big difference:

sudo sysctl debug.lowpri_throttle_enabled=0
Don't forget, though, to do the same command but with enabled=1 after the backup is done.
  • Like
Reactions: BigMcGuire