Optimizations for slow server?

Hey, been running UrBackup for a few years now and it’s been wonderful! Running the server on a Banana Pi M1 — dual core CPU, 1GB RAM, Gigabit Ethernet, SATA HDD — and noticed the main bottleneck is server CPU usage (no surprises there). I’ve also noticed that it barely uses any RAM, with htop showing only 7% memory usage (so 70MB? Not completely sure how to interpret these readings).

Currently backups run at around 100-160 Mb/s (which is already surprisingly good given the dated and slow CPU), and I was just wondering if there are any recommended optimizations to reduce load on the server end, possibly offloading it to the client? So far I’ve disabled VHD compression and backups are being stored in an uncompressed ext4 partition. All transfer modes have also been set to ‘raw’.

I’m not expecting there to be any further steps, but if anyone knows of any optimizations I’ve missed I’d greatly appreciate it.