First off, lesson learned, no more small pre-built external HDDs. Got it.

These are the 3 HDDs I want to use in my Unraid server:

1x 1TB wdbkuz0050bbk-ea, MB: 771801-002 Rev A (meh on this one actually, 1TB is nothing nowadays)
2x 5TB wdbbep0010bbk-01, MB: 800041-003 Rev P1

I've searched around for the past couple of days and I've found things that make it look easy and others that make it seem like it is its own rabbit hole.

I decided to test the procedure on the 771801 board 1st, since it's the least important drive, using this YT vid:
https://www.youtube.com/watch?v=L_LVrQ20Geg

I connected the drive to my W11 PC using a SATA-USB adaptor (without really thinking about how it's connecting back to USB again) and Disk Management wanted to format it. I hesitated at 1st but then decided I don't really care about the data on it (I'm ONLY interested in USE and didn't want to deal w/ the PITA decryption) and formatted the drive. Tested transferring files to it and it averaged out at about 100MB/s.

I then realized the USB adaptor influenced speeds and directly connected the drive to the same computer after powering it down. The speeds are now atrocious. They start AMAZING (1.5GB/s) but then trickle down to 30-50MB/s in a few seconds. I used the same folder from my Desktop and also reformatted, JIC.

Figured this would be a great point to see if someone could give me some advice on my specific situation.

I'm guessing those are SMR drives, which would account for the poor write performance.

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A backup a day keeps DR away.

The 5TB model numbers are both WD50NDZW-11MR8S1, while the 1TB is a WD10JMVW-11S5XS0. Googling those model numbers with "SMR", I found pages saying they are as you predicted.

Does this mean max performance is already achieved through USB? I REALLY loved the idea of using my soldering skills to reclaim the 'shuckability' of these drives :/

An SMR drive bogs down during sustained writes because its CMR cached areas fill up. You could run a HD Tune read benchmark against each drive. That should give you a graph showing the max and min transfer rates at the innermost and outermost cylinders. If the USB interface were limiting the drive's read performance, you would see a flat plateau at the outermost cylinders.

_________________
A backup a day keeps DR away.

Is there any way that my soldered-on SATA port can achieve speeds greater than the 100MB/s I get through the USB port of the drive's motherboard?

I had the 5tb drives connected to my Unraid server as part of the array and they slowed it down because everything then had to run at USB speed. I replaced them with 3.5 SATA drives and the server is running much faster.

I'd love to re-add them to the server using SATA speeds, but if not I'll just make them off-site backups.

It's not a connectivity issue its a storage technology one. SMR drives can't sustain transfer speeds, nothing you can do can change that, you will need to buy none SMR drives if you want better performance.

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Data Recovery Services in the UK.
https://www.usbrecovery.co.uk/

Device-Managed Shingled Magnetic Recording (DMSMR):
https://blog.westerndigital.com/dmsmr-device-managed-shingled-magnetic-recording/
https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/collateral/white-paper/white-paper-shingled-magnetic-recording-hdd-technology.pdf


Basically this means that under conditions where there is no idle time (ie sustained writing), the drive runs out of resources (ie CMR cache) and starts to slow down (because it needs to flush the cache).

_________________
A backup a day keeps DR away.

Thanks for the replies.

I've come to terms that they're stuck on their USB ports. I'm going to use them as rotating off-site backs up.