My 2TB WD on DS213j is full. Too many Blueray backup. My DS213+ no longer able to backup to DS213j.
Not a good sign.
So buy myself a new 6TB hard disk at price HKD$2380. It is a bit expensive but worth it. Stability is the most important thing for backup media.
My WD 2TB hard disk already running 7×24 on ds213j for 3.5 years. I believe the new 6TB can last for another 5 years, at least.