PCIe USB3.0 Controller - slow write speed to SSD

Hello,

I have a problem with all my PCIe USB3.0 controllers running on Debian 10.3 64x -

kernel 4.19.0-8 and the backports kernel 5.3.x

They all have diffrent chipsets: VLI805, uPD720201, ASM1042A (latest firmware).

I got on all those controllers the same issue:

I only get 60-80MB/s write speed to the USB 3.0 SSD.

The transfer speed is not steady if i can trust "nmon".

Only bursts of data geting transfered. Then it sits in idle for about 3 seconds and does nothing.

I'm getting 300MB/s write speed on windows. I have no issue with the read speed (300MB/s) on Debian.

I already tried follow:

- blacklisted uas -> lsblk didn't even show the USB3.0 SSD

- kernel parameters : iommu=soft intel_iommu=off pci=nomsi -> didn't change anything

Tested on follow hardware:

CPU: 2x Intel Xeon L5640

MB1: Tyan S7012 (EOL, latest BIOS)

MB2: Supermicro X8DTH-I (EOL, latest BIOS)

SSD(internal): 2x Adata SU800 1TB (SATAII AHCI) (software raid 1 mdadm)

SSD(usb): 2.5" enclosure - Samsung 850 Evo 256GB (latest firmware on enclosure and ssd)

It is old hardware, i know that, but i never had a issue like this on linux.

All old hardware that i had run flawless on linux even when there was no drivers for windows anymore.

Maybe this is a bug. But i need to be sure.

Do you need more information? Just tell me.

Thanks alot,

Patrick

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