A very slow external hard drive after the High Sierra10.13.3 Update

I'm having a very similiar problem. I won't get started in my RAID enclosure issues, BUT my external drives that ran at 80/90MB/s on 10.12.4 are only running at 40MB's now. As a pro video editor thats unacceptable. My Thunderbolt drives that ran at 220MB/s are down to 180MB/s

My RAID used to run at 250MB/s via USB on my old MacPro and now refuses to run via USB at all on my $8000 iMac Pro (10.13.3) Via firewire and adapters it's down to 20MB/s.

This is all on Apple and is beyond unacceptable.

Cool, thanks for the link. I tried actually talking to them (in a very calm and reasonable tone) more about my issue and what I found with it working but I got transferred to a dead extension on 2 separate occasions. I asked to speak with the person who was in charge of my case as well and got transferred to another dead extension. I feel like I touched on a nerve and the more I look through the depths of the internet I'm finding not only USB issues but USB HW RAID issues with 10.13 from a lot of folks in my situation.

Anyways, thanks for the link. I'll email them in hopes this gets addressed.

You can let Apple know here:

Product Feedback - Apple

These are just user-to-user forums and although Apple moderates here, they aren't reading the comments or participating in the discussion.

Have you run Disk Utility > First Aid on your external and what does it report?

Is there another port that you can plug the drive and test?

It may be a drive that is headed south. I wouldn't rely on it as my only backup.