[Help] D4‑320 Drive Throughput Fluctuations – Sustained Speeds Drop After Transfers

[kekalot]

Hi TerraMaster team,

I’ve been testing my D4‑320 with IronWolf Pro drives and noticed some inconsistent performance that I wanted to check with you.

Previously, one drive would do ~240 MB/s and the second ~85 MB/s from the same source (Barracuda drive). I moved the IronWolf Pro from the 2nd slot to the 3rd and restarted the DAS — after that, both drives reached ~240 MB/s.

Both drives sustained ~240 MB/s for several hours, but after completing one queued transfer and starting a second, both dropped to ~150–165 MB/s.

Restarting the DAS again didn’t change this. The source drive type (HDD or SSD) also didn’t affect the behavior.

TL;DR: Drives can reach 240 MB/s, but then speed drops to ~170 MB/s (or ~85 MB/s earlier). I’m using the cable that came with the DAS, and I’m copying to/from one drive at a time.

Is this normal for the D4‑320? Could the DAS be re-negotiating speeds, or is something else affecting sustained throughput?

I’m happy to provide more details or test results if needed.