When the primary MDS is downed, readied secondary MDS changes into primary MDS automatically, and operation is continued. The processing in this case is shown below.
Switching the secondary MDS to the primary MDS
The secondary MDS operates as the primary MDS in place of the primary MDS that has failed.
The new primary MDS replays the update log to ensure consistency of the file system.
Resuming processing after MDS switching
The AC sends a processing request to the new primary MDS. Until that request is accepted, all access to the file system is blocked.
Restarting the failed MDS
Usually, the MDS is restarted as the secondary MDS.
