Yesterday I was notified that TimeMachine hadn’t successfully backed up for over 17 days, today I was notified it would take 3 days to perform a new back-up. Something had to be wrong somewhere, but what? And how could I reduce the time to complete the backup?
I think I’ve mentioned before that we have a Western Digital ‘My Cloud Backup’ unit on our home network which acts as a TimeMachine target. However in our Victorian house Wi-Fi connectivity isn’t as easy as it might be so the NAS is upstairs connected to a Wi-Fi extender, whereas the laptop was downstairs on the main hub. So when TimeMachine was going to take so long to complete a ~65GB backup that it couldn’t actually estimate a time, I decided to log on to the NAS and see what was going on.
The MyCloudBackup management page is actually quite informative and gives a real-time network monitor as one of the many utilities. In my case it was barely averaging 1MB/s – no wonder the backup was going to take an indefinitely long time to complete!
Eventually I found a couple of tricks which have increased the transfer speed by more than 10-fold.
Remove The TimeMachine Throttle
By default TimeMachine is throttled by macOS so as not to take too many CPU cycles away from whatever you’re actually working on. However you can temporarily remove this throttling using the following command-line from the Terminal:
sudo sysctl debug.lowpri_throttle_enabled=0
Changing this setting allows TimeMachine to run at full capacity – it might impact your other open apps, but it means the backup will complete faster. Note that it will only last until you reboot however, or you actively change it back by changing the ‘0’ to ‘1’.
Move The Laptop Closer to the NAS
This should have been my first port of call really, however it took me a while to realise that, although the NAS is connected to the Wi-Fi extender via gigabit LAN cabling, the laptop was connected on 2.4GHz to a hub, which was then connected, also via 2.4GHz to the Wi-Fi extender upstairs.
Fortunately the Wi-Fi extender also broadcasts a 5GHz signal which is reachable from downstairs. By moving the laptop onto this signal, and thus removing a couple of hops (not to mention slow network speeds) the backup speed increased substantially.
All told, the combination of these changes increased the traffic speed measured on the NAS from ~1MB/s to over 11MB/s and the estimated time to completion in TimeMachine dropped from an unknown value, to about 2 hours!
So the moral of the story – remove unnecessary network hops, use the fastest connection available and temporarily remove throttling and your backups will run silky smooth 😉