Unbelievably slow file transfer speeds

I had a previous issue which made me decide to reinstall Manjaro. I moved my home directory to an HDD, then put a fresh install on my M.2 drive. I am transferring about 700GB of games and media via overwriting the new home directory with the old one from the HDD.

When it starts out, it transfers at a reasonable rate for sending from a a 7200rpm HDD to a SATA M.2 directly on the hard drive, about 170mib/s, implying the transfer will take roughly an hour. Unfortunately, after a few minutes, it drops down to about 20, then 12, then 2, and now it is transferring at 500kbps implying the transfer will take roughly 300 hours. It jumps back up to 2 and sometimes as high as 12. This is a click and drag via Thunar, if that matters.

-Yes, fstrim.timer is running
-No, neither of these drives are connected via USB, don’t be silly
-No, nothing is being transferred via network

Any tips? My winman is i3 on both the new and old install.

Update: Transfer speed has, after about 20 minutes, returned to about 140mbps. Very strange.

Not really strange… depending on how much RAM you have it writes first at full speed to the RAM, while it writes constantly with full speed in the background to the disk . I guess you are confused (and you are not the only one) because the file manager just reports the transfer speed of DISK → RAM, but not RAM → DISK.

Dirty Pages are 10% of your RAM.

sudo sysctl -a | grep vm.dirty

You can check it live with iotop for example.

You can read more about it here: Decrease dirty bytes for more reliable USB transfer

Maybe it helps to understand the background a bit.

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this is really weird! So it was low, and then suddenly it got fixed?