Replaced 2 x 4TB with 2 x 8TB, VERY SLOW R+W speeds!

I recently replaced 2 x 4TB HDD disks with 2 x 8TB HDD disks into my:

G-Technology 8TB G-Raid with Thunderbolt 3, USB-C (USB 3.1 Gen 2), and HDMI, Removable Dual Drive Storage System, Silver - 0G05748

I created a RAID1 (mirror) as with my last 2 x 4TB set up.

RESULT: EXTREMELY slow read/write speeds. Averaging < 125 MB/s.


  • I am using the requisite Thunderbolt 3 cable from my external drive and into the computer
  • The drives are brand new + high quality brand.
  • Also, I’m on a Mac Studio M2 Max, very capable of handling high-speed I/O devices
  • I am able to R/W data from the drives, abeit SLOWLY
  • I am using the entire set up as a backup to my SSD; CC Cloner talks to it successfully
  • I DID have an issue with my last set of drives, hence the replacement (while I was at it I upped the storage—from 4TB to 8TB for each bay)
  • The older 4TB drives now seem to read well on another device (a dual dock) and have decent R/W speeds

QUESTIONS: Any idea why I am experiencing very low r/w speeds? Is it a chassis issue? Would a chassis fault CAUSE extremely low R/W speeds? Any trouble shooting? Any solutions?

1 Like

Hi @dastoelk,

Have you opened a Support Case? If not opened, for more information, please contact the WD Technical Support team for the best assistance and troubleshooting: