Recently came across this post on twitter and I thought it was a pretty solid tip, so here it is. To disable the default throttling that causes backups to be slow use this terminal command:

sudo sysctl debug.lowpri_throttle_enabled=0

The problem is that this setting is forgotten every time you reboot, so to fix that you gotta add a script that runs when you boot up your computer, so with this command you’ll make the script file and open it in an editor on your terminal:

sudo nano /Library/LaunchDaemons/nothrottle.plist

Then paste the following text into that file:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "">
<plist version="1.0">

After you’ve pasted the text into the file, to exit back to the terminal use ⌃O then hit enter and finally ⌃X. Then use the following command to enable the script to run when your computer boots:

sudo chown root /Library/LaunchDaemons/nothrottle.plist;sudo launchctl load /Library/LaunchDaemons/nothrottle.plist

If in the future you want to undo these changes, all you need to do is use the following command and reboot afterwards.

sudo launchctl unload -w /Library/LaunchDaemons/nothrottle.plist