I have several generations of NAS from QNAP. I have a, maybe not good, habit of putting them into sleep mode every night. Because there is no one access them overnight, it really help to reduce the noise and not bring much jobs, like entering password for unlocking, other than press the power button to resume.
Several months ago, I brought a new one, TS-873A, found there is no sleep function left. I contacted some other users, who use other new models as well. No one see such a function any more. To make sure it is, I fired a ticket to the help desk, the answer is the same — sleep function is no more supported.
The official documentation says nothing about this change. By searching the reason why sleep mode is missing, only one article saying that SED SSD Storage Pool does not support the S3 Sleep function. But actually, all kinds of SSD/HDD cannot have a good sleep in new models at all.
I don’t know the reason but leave this as a notice to the ones who want to buy a new NAS from QNAP.