Ceph » CephFS

Currently if standby for current fs is not available the mon will look for standby for another fs. Although it makes sense for some users this behaviour may not be disarable.

Consider a situation with many fs volumes, each has active and standby mds. Then for one volume a corruption is introduced that makes the active mds to crash. The mon will chose all available standby mds until all them crash and after the systemd will disable mds restart due to frequent crashes we will endup with no standby mds available for any fs. Some users find this undesirable because:

1) a corruption on one fs potentially affect other fs
2) when an mds from another fs is used as active it may be confusing (e.g. it is difficult to find out for what fs an error is in the mds log)

So some users would prefer to disable this behavior, e.g. via a config or fs (fsmap) option.