Slow backing up over the network
I’ve set Monterey’s Time Machine to back up my MacBook Pro wirelessly to a shared disk on my Mac mini, which also connects wirelessly to my Wi–Fi router. How can I get backups to run faster, as they’re taking an age?
If both Macs are connecting over Wi–Fi, then this will significantly reduce the speed of transferring the files in a backup between them, as both Macs are contending for the same wireless connections with your router.
If you’re going to use a shared disk or a network–attached storage (NAS) system for Time Machine backups, then you should connect it to your router using wired Ethernet, as that will improve transfer speeds considerably. The very fastest are achieved when the Mac backing up is also hooked up by wire, something worthwhile for large initial backups and other occasions when there’s a lot to be transferred.
One quick test worth doing is to copy a large file, say around 10GB, between the two Macs using the Finder. Time how long that takes, and divide the file size in MB by the time in seconds to give a transfer rate in MB/s. That’s the fastest transfer rate that Time Machine is likely to achieve when backing up using that network connection, and it’s more likely to run at around two– thirds of that much of the time.
In practice, relying only on Wi–Fi connections is likely to work satisfactorily for small hourly backups of less than a few gigabytes, but will most likely be too slow for hundreds of gigabytes.