SMB Transfers Freezes Whole Mac Disk From Reading

After a couple gigs into copying to an SMB (using Unraid for production work) - the transfer grinds to a halt, and the everything on Mac becomes very slow. It seems the disk reads themselves stop for 10 seconds or so at a time, resume for 3 and stop again.

I read about a bug like this back with Mojave but it was patched soon after and not mentioned again.

Oddly if I start compressing a file - the transfer begins flying right on through and everything works fine until compression finishes. Furthering my suspicion into MacOS locking up the main disk.

Attached photo - notice the burst of IO but the last third is when I started compressing a file

Some details -

• MacOS 12.1 on a MBP 2018 with a 2.9ghz i9
• Using a 10g ethernet (bought thinking my previous interface was the problem)
• Unraid 6.9.2 - also 10g ethernet. Copy from windows works fine
• Speeds burst at 900mbps to 2Gbps for a few seconds and dive to 6kbps about 12 seconds at at time, during which things like launching an app get a beachball until disk reads resume