Steam downloads are so slow on the NVMe, but faster on the SATA SSD.

[pink]

Help!

I have two SSDs: one is a new WD Green 480GB SN350, and the other is a SATA SSD Kingston 240GB, which currently has only 9% health. When I try to download games to my SATA SSD, the speed is much faster, 400-700 MB/s. However, on my NVMe SSD, the initial speed is very high, but after about 20 seconds, it drops to around 50 MB/s. If I restart Steam, the speed goes back up, but then slows down again. I really can’t understand what’s happening.

And obviously, my NVMe SSD is usually faster overall, but the problem only occurs with Steam.

[Elucidator]

Western Digital NVMe SSDs has some kind of problem with "Write Caching on the Device". Disable that.
Windows 11 by default has Bitlocker Drive Encryption enabled, which slows down the SSD by 60% and causes everything to be encrypted before placed on the SSD, which, means a slowdown.
SSDs don't like file indexing (it slows them down slightly). For HDDs it works well.
Disable Sysmain. (a service in windows) ... it's also more of a slow down on SSDs

Power Management settings need to be set to performance, otherwise all of the "economic mode", "green power mode" and "power saving stuff" build into windows will be switched on, which means, if windows sees no need, it slows stuff down

You also need to set this per driver. (yes, each driver has its own settings) for maximum performance at least.

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Windows considers Steam a background task because its download is launched by the background service "Steam Client Service"-- which is why User Tasks are prioritized and steam ends up being slower by default unless you're doing nothing on the system.
It comes with the upside that you can watch youtube or netflix undesturbed without needing to limit the download speed though.

Also make sure you check your network controller software if you have any. There may be some auto tuning features in there set to .... slow down steam basically.