Don't notice this much.... disk is usually the bottleneck, and otherwise it will be the network to the remote backup location. Still backups complete in seconds:

Repository: ssh://backup/./backups/mungedhostname.borg Archive name: 20220327-2201 Archive fingerprint: 8b710144579c8d531e7c4a0192304323081b14a71445557608d859494bbe84b6 Time (start): Sun, 2022-03-27 22:01:35 Time (end): Sun, 2022-03-27 22:01:52 Duration: 17.28 seconds Number of files: 45678

Original size Compressed size Deduplicated size This archive: 24.22 GB 9.35 GB 47.78 MB All archives: 363.60 GB 140.91 GB 7.81 GB

Unique chunks Total chunks Chunk index: 59857 852257

Sure, for spinning disks, but deduplication, compression, and encryption can easily be the bottleneck if you have some NVMEs.

And you can turn the compression way up to where it is very expensive but gives much better space savings.

I agree that a multithreaded borg could utilise resources better, esp. IF you have a lot of changed / new data to back up.

But OTOH, for many users this is primarily the case for the first backup, but not for their daily / hourly backups when most files are unchanged - for that, I guess speed is I/O bound and all your CPU cores won't help you with that.

So for N-1 backup runs, it just works good enough already for many users. And for that 1 initial backup, some patience helps. :-)

Implementing MT is planned since long, but due to the above, other stuff had higher priority.

You could spread the backup into several isolated borg repos and run in parallel if CPU is the bottleneck.

I like that it runs in the background without heating my laptop much.