The way I read it, the message reads this way:
Dec 30 19:08:55 syno_hdd_util:
in [/dev/hda] is not ssd
it seems it is saying that the device is not an SSD (Solid-State Drive)
What is the context of this message (where and how did it appear)?
What is the Samsung HD400LD? e.g. is it your internal HD, external HD, etc.?