This document is for a development version of Ceph.
MDS Autoscaler Module¶
The MDS Autoscaler Module monitors
fsmap update notifications from the mgr
daemon and takes action to spawn or kill MDS daemons for a file-system as per
changes to the:
standby promotions to active MDS state in case of active MDS rank death
Bumping up the
max_mds config option value causes a standby mds to be promoted
to hold an active rank. This leads to a drop in standby mds count. The MDS
Autoscaler module detects this deficit and the orchestrator module is notified
about the required MDS count. The orchestrator back-end then takes necessary
measures to spawn standby MDSs.
max_mds config option causes the orchestrator back-end to kill
standby mds to achieve the new reduced count. Preferably standby mds are chosen
to be killed when the
max_mds count is dropped.
An increment and decrement of the
standby_count_wanted config option value
has a similar effect on the total MDS count. The orchestrator is notified about
the change and necessary action to spawn or kill standby MDSs is taken.
A death of an active MDS rank also causes promotion of a standby mds to occupy the required active rank. The MDS Autoscaler notices the change in the standby mds count and a message is passed to the orchestrator to maintain the necessary MDS count.
NOTE: There is no CLI associated with the MDS Autoscaler Module.