Ceph has a number of flags that are usually applied across the cluster as a whole. These flags direct Ceph's behavior in a number of ways and when set are reported by ceph status.
The most commonly utilized flag is noout, which directs Ceph to not automatically mark out any OSDs that enter the down state. Since OSDs will not be marked out while the flag is set, the cluster will not start the backfill / recovery process to ensure optimal replication. This is most useful when performing maintenance, including simple reboots. By telling Ceph Hold on, we'll be right back we save the overhead and churn of automatically-triggered data movement.
Here's an example of rebooting an OSD node within a Jewel cluster. First we run ceph -s to check ...
