Hi Takashi A couple of things to note: 1) I've had a look at all the drives I have tested under Windows using Crystaldiskinfo and curiously the pair of WD 2TB don't show the APM flag while all others do. 2) I noticed both WD 2TB drives have Grub2 bootloaders in their MBRs - an overhang from previous configurations that I forgot to get rid of. I've checked journalctrl and there appears to be no kernel problems regards these drives, if you want the logs I can post. I tried no_console_suspend=1 in kernel boot parameters but makes no difference, I assume I did that correctly ? Thanks