Hi, I just received a new WD_BLACK D10 12Tb mounting the HC520 HGST HUH721212ALE604 .
I noticed that transfer speeds drop quite a lot when adding data to the disk.
Also, my read speeds are always slower than my write speeds but reviews online from 2020 always show matching read/write speeds.
After having added 2Tb of data to it, my writes/reads dropped (also see the slower read speeds):
When doing a full surface scan, I noticed that the speeds started at 230MB/s and dropped to 179Mb/s at 3Tb, 173Mb/s at 6Tb and 120Mb/s on the last Terabyte.
Is such speed deterioration normal? Is this within tolerance or should I request a replacement?
The speed drop you’re experiencing is normal for HDDs, especially large-capacity drives like the WD_BLACK D10 with the HGST HC520. Here’s why:
- Data Density: Outer tracks (near the start of the disk) are faster as they store more data per revolution. Speeds drop as the head moves to inner tracks.
- Fragmentation & Load: As data fills up, fragmentation and higher load can impact write/read performance.
Your speeds (230 MB/s to 120 MB/s) are within expected ranges for this drive. A replacement isn’t necessary unless there are other issues like frequent disconnects or unusual noises.
If you see my post, why is the read speed lower than the write speed on my disk?
Asking because every single review I have seen online from 2020 show that there are always equivalent read and write speeds.
See for instance this ATTO result: WD Black D10 Game Drive for Xbox 12TB Review
