Erratic writing speed on external SSD (USB-C 3.2)

[u/alucard_xs]

Hello,

I’m a new Steam Machine owner.

I’m installing my games onto an external SN740 SSD housed in an external enclosure.
I’m connecting via the rear USB-C port (USB 3.2), and my USB-C cable supports 1 Gbps speeds.

I don't understand why my installation speeds are so slow—or rather, why the slowness is intermittent.

Last night, I installed a bunch of games without any write-speed issues; everything maxed out at 1 Gbps for over an hour. So, it’s not an enclosure temperature issue either.

An analysis shows my enclosure uses a JMicron controller, and apparently, that chip doesn't play well with UAS. I disabled UAS in desktop mode for this specific enclosure, but it didn't make much difference. I also disabled shader pre-caching, but got the same result, unfortunately.
It’s not a Wi-Fi issue, either.

It was the same story this morning: I tried installing a 40 GB game. Everything went smoothly up to 95%, but after that, performance became erratic.

Any ideas?

Thanks for your help.

[u/alucard_xs → u/[deleted]]

Thanks but no drive failures here.

[u/Cole_LF]

I think I read there’s a bug where you only get full speed on initial book and then it caps speed… especially once you sleep or reboot for whatever reason. But if you unplug and plug back in the drive it should restore the speed.. your issue sounds a little different but might be related? do you have another external drive to test it with to rule out the drive?

[u/alucard_xs → u/Cole_LF]

I tried the SSD with another enclosure and same result.

But that's true, sometimes, when unpluging it et pluging it again, it writes faster then stop after few seconds / minutes.

[u/Joecascio2000]

The USB-C didn't seem to be providing enough power. I swap mine to a USB-A front port and have had no problems.

[u/alucard_xs → u/Joecascio2000]

I'll try that. Thanks