[ceph-users] One PG is stuck and reading is not possible

ceph version 12.2.13 luminous (stable) My whole ceph cluster went to kind of read only state. Ceph status showed that client reads is 0 op/s for whole cluster. There was normal amount of writes going on. I checked health and it said: # ceph health detail HEALTH_WARN Reduced data availability: 1 pg inactive, 1 pg peering PG_AVAILABILITY Reduced data availability: 1 pg inactive, 1 pg peering pg 26.13b is stuck peering for 25523.506788, current state peering, last acting [2,0,33] All osds showed to be up and all monitors are good. All pools are 3/2 (size/min) and space usage ~30%. I fixed this by restarting forst osd.2 (nothing happened) and then restarted osd.0. After that everyting went back to normal. So what can cause "stuck peering" and how can i prevent this event from happening again?