Time capsule wired backup transfer slow with fast "bursts"
Time Machine runs as a low priority process by default, and this will cause it to be throttled whenever a higher priority process runs (and possibly to optimize energy usage on battery), hence the performance bursts.

You can disable throttling for Time Machine with:

sudo sysctl debug.lowpri_throttle_enabled=0


Keep in mind this might increase power usage on battery.

This setting will be lost on reboot. To make it permanent, create a launch daemon:

sudo nano /Library/LaunchDaemons/nothrottle.plist


Enter this text in the file:

&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"&gt;
&lt;plist version="1.0"&gt;
&lt;dict&gt;
&lt;key&gt;Label&lt;/key&gt;
&lt;string&gt;nothrottle&lt;/string&gt;
&lt;key&gt;ProgramArguments&lt;/key&gt;
&lt;array&gt;
&lt;string&gt;/usr/sbin/sysctl&lt;/string&gt;
&lt;string&gt;debug.lowpri_throttle_enabled=0&lt;/string&gt;
&lt;/array&gt;
&lt;key&gt;RunAtLoad&lt;/key&gt;
&lt;true/&gt;
&lt;/dict&gt;
&lt;/plist&gt;


Save it and exit nano (Press ctrl+X, then Y when asked to save changes)

Then enable the launch daemon:

sudo chown root /Library/LaunchDaemons/nothrottle.plist

sudo launchctl load /Library/LaunchDaemons/nothrottle.plist


Backups should now be performed at maximum performance.



In case you want to re-enable throttling, run:

sudo sysctl debug.lowpri_throttle_enabled=1


If you had enabled the launch daemon, run:

sudo launchctl unload /Library/LaunchDaemons/nothrottle.plist


Source