You already have a unhealthy cluster before you do the reboot. Status should be HEALTH_OK before you start any maintenance work.
osdmap e845: 7 osds: 2 up, 2 in; 8 remapped pgs
So you have 7 OSD's (HDD's) and only 2 of them are online/working!? Also 1 mon is down. You have 4 mons, so when you...