# Common states

up:active This is the normal operating state of the MDS. It indicates that the MDS and its rank in the file system is available.

up:standby The MDS is available to takeover for a failed rank (see also :ref:mds-standby). The monitor will automatically assign an MDS in this state to a failed rank once available.

up:standby_replay The MDS is following the journal of another up:active MDS. Should the active MDS fail, having a standby MDS in replay mode is desirable as the MDS is replaying the live journal and will more quickly takeover. A downside to having standby replay MDSs is that they are not available to takeover for any other MDS that fails, only the MDS they follow.

up:boot This state is broadcast to the Ceph monitors during startup. This state is never visible as the Monitor immediately assign the MDS to an available rank or commands the MDS to operate as a standby. The state is documented here for completeness.

up:creating The MDS is creating a new rank (perhaps rank 0) by constructing some per-rank metadata (like the journal) and entering the MDS cluster.
up:starting The MDS is restarting a stopped rank. It opens associated per-rank metadata and enters the MDS cluster.
up:stopping When a rank is stopped, the monitors command an active MDS to enter the up:stopping state. In this state, the MDS accepts no new client connections, migrates all subtrees to other ranks in the file system, flush its metadata journal, and, if the last rank (0), evict all clients and shutdown (see also :ref:cephfs-administration).
up:replay The MDS taking over a failed rank. This state represents that the MDS is recovering its journal and other metadata.

up:resolve The MDS enters this state from up:replay if the Ceph file system has multiple ranks (including this one), i.e. it’s not a single active MDS cluster. The MDS is resolving any uncommitted inter-MDS operations. All ranks in the file system must be in this state or later for progress to be made, i.e. no rank can be failed/damaged or up:replay.

up:reconnect An MDS enters this state from up:replay or up:resolve. This state is to solicit reconnections from clients. Any client which had a session with this rank must reconnect during this time, configurable via mds_reconnect_timeout.

up:rejoin The MDS enters this state from up:reconnect. In this state, the MDS is rejoining the MDS cluster cache. In particular, all inter-MDS locks on metadata are reestablished.
If there are no known client requests to be replayed, the MDS directly becomes up:active from this state.

up:clientreplay The MDS may enter this state from up:rejoin. The MDS is replaying any client requests which were replied to but not yet durable (not journaled). Clients resend these requests during up:reconnect and the requests are replayed once again. The MDS enters up:active after completing replay.
down:failed No MDS actually holds this state. Instead, it is applied to the rank in the file system
down:damaged No MDS actually holds this state. Instead, it is applied to the rank in the file system
down:stopped No MDS actually holds this state. Instead, it is applied to the rank in the file system

• handle_mds_map state change up:boot –> up:replay
• handle_mds_map state change up:replay –> up:reconnect
• handle_mds_map state change up:reconnect –> up:rejoin
• handle_mds_map state change up:rejoin –> up:active

## State Diagram

This state diagram shows the possible state transitions for the MDS/rank. The legend is as follows:

### Color

• 绿色: MDS 是活跃的.
• 橙色: MDS 处于过渡临时状态，试图变得活跃.
• 红色: MDS 指示一个状态，该状态导致被标记为失败.
• 紫色: MDS 和 rank 为停止.
• 红色: MDS 指示一个状态，该状态导致被标记为损坏.

### Shape

• 圈：MDS 保持这种状态.
• 六边形：没有 MDS 保持这个状态.

### Lines

• A double-lined shape indicates the rank is “in”.