Metadata Server daemon states
By default, a Ceph File System uses only one active MDS daemon. However, systems with many clients benefit from multiple active MDS daemons.
The Metadata Server (MDS) daemons operate in two states:
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Active: manages metadata for files and directories stores on the Ceph File System.
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Standby: serves as a backup, and becomes active when an active MDS daemon becomes unresponsive.
You can configure the file system to use multiple active MDS daemons so that you can scale metadata performance for larger workloads. The active MDS daemons dynamically share the metadata workload when metadata load patterns change. Systems with multiple active MDS daemons still require standby MDS daemons to remain highly available.
What happens when the active MDS daemon fails
When the active MDS becomes unresponsive, a Ceph Monitor daemon waits a few seconds equal to the
value specified in the
mds_beacon_grace option. If the active MDS is still
unresponsive after the specified time period has passed, the Ceph Monitor marks the MDS daemon as
laggy. One of the standby daemons becomes active, depending on the
configuration.Note: To change the value of
mds_beacon_grace, add this option to the
Ceph configuration file and specify the new value.