I obtained several Raspberry pi 2’s and noticed that the main NAS a DS213j and the secondary NAS DS101j (only used for backups) were not going to sleep.
Secondary NAS issue
After a lot of investigation. I concluded that the primary MAS was waking up the secondary NAS. As I am really using the secondary NAS to prevent the use of Wannacry and alike I decided to disable Samba on it. Thus the only way to access it now is via ssh or rsync (which is used for the backups)
Primary NAS issue
This was not sleep due to
a) A raspberry pi running plex repeatedly interrogating my music library.
b) Installed software did not allow the disks to go to sleep. Re Surveillance station which I removed as was not now necessary.
I can now see in the primary NAS logs the disks are periodically being woken from sleep.
And the secondary NAS which is quite noisy now remains silent all the time except at 3am in the morning when the backups occur.