Appendix B. Metadata Server daemon configuration Reference Refer to this list of commands that can be used for the Metadata Server (MDS) daemon configuration. mon_force_standby_active Description If set to true , monitors force MDS in standby replay mode to be active. Set under the [mon] or [global] section in the Ceph configuration file. Type Boolean Default true max_mds Description The number of active MDS daemons during cluster creation. Set under the [mon] or [global] section in the Ceph configuration file. Type 32-bit Integer Default 1 mds_cache_memory_limit Description The memory limit the MDS enforces for its cache. Red Hat recommends using this parameter instead of the mds cache size parameter. Type 64-bit Integer Unsigned Default 4294967296 mds_cache_reservation Description The cache reservation, memory or inodes, for the MDS cache to maintain. The value is a percentage of the maximum cache configured. Once the MDS begins dipping into its reservation, it recalls client state until its cache size shrinks to restore the reservation. Type Float Default 0.05 mds_cache_size Description The number of inodes to cache. A value of 0 indicates an unlimited number. Red Hat recommends to use the mds_cache_memory_limit to limit the amount of memory the MDS cache uses. Type 32-bit Integer Default 0 mds_cache_mid Description The insertion point for new items in the cache LRU, from the top. Type Float Default 0.7 mds_dir_commit_ratio Description The fraction of directory that contains erroneous information before Ceph commits using a full update instead of partial update. Type Float Default 0.5 mds_dir_max_commit_size Description The maximum size of a directory update in MB before Ceph breaks the directory into smaller transactions. Type 32-bit Integer Default 90 mds_decay_halflife Description The half-life of the MDS cache temperature. Type Float Default 5 mds_beacon_interval Description The frequency, in seconds, of beacon messages sent to the monitor. Type Float Default 4 mds_beacon_grace Description The interval without beacons before Ceph declares a MDS laggy and possibly replaces it. Type Float Default 15 mds_blacklist_interval Description The blacklist duration for failed MDS daemons in the OSD map. Type Float Default 24.0*60.0 mds_session_timeout Description The interval, in seconds, of client inactivity before Ceph times out capabilities and leases. Type Float Default 60 mds_session_autoclose Description The interval, in seconds, before Ceph closes a laggy client's session. Type Float Default 300 mds_reconnect_timeout Description The interval, in seconds, to wait for clients to reconnect during a MDS restart. Type Float Default 45 mds_tick_interval Description How frequently the MDS performs internal periodic tasks. Type Float Default 5 mds_dirstat_min_interval Description The minimum interval, in seconds, to try to avoid propagating recursive statistics up the tree. Type Float Default 1 mds_scatter_nudge_interval Description How quickly changes in directory statistics propagate up. Type Float Default 5 mds_client_prealloc_inos Description The number of inode numbers to preallocate per client session. Type 32-bit Integer Default 1000 mds_early_reply Description Determines whether the MDS allows clients to see request results before they commit to the journal. Type Boolean Default true mds_use_tmap Description Use trivialmap for directory updates. Type Boolean Default true mds_default_dir_hash Description The function to use for hashing files across directory fragments. Type 32-bit Integer Default 2 ,that is, rjenkins mds_log Description Set to true if the MDS should journal metadata updates. Disable for benchmarking only. Type Boolean Default true mds_log_skip_corrupt_events Description Determines whether the MDS tries to skip corrupt journal events during journal replay. Type Boolean Default false mds_log_max_events Description The maximum events in the journal before Ceph initiates trimming. Set to -1 to disable limits. Type 32-bit Integer Default -1 mds_log_max_segments Description The maximum number of segments or objects in the journal before Ceph initiates trimming. Set to -1 to disable limits. Type 32-bit Integer Default 30 mds_log_max_expiring Description The maximum number of segments to expire in parallels. Type 32-bit Integer Default 20 mds_log_eopen_size Description The maximum number of inodes in an EOpen event. Type 32-bit Integer Default 100 mds_bal_sample_interval Description Determines how frequently to sample directory temperature when making fragmentation decisions. Type Float Default 3 mds_bal_replicate_threshold Description The maximum temperature before Ceph attempts to replicate metadata to other nodes. Type Float Default 8000 mds_bal_unreplicate_threshold Description The minimum temperature before Ceph stops replicating metadata to other nodes. Type Float Default 0 mds_bal_frag Description Determines whether or not the MDS fragments directories. Type Boolean Default false mds_bal_split_size Description The maximum directory size before the MDS splits a directory fragment into smaller bits. The root directory has a default fragment size limit of 10000. Type 32-bit Integer Default 10000 mds_bal_split_rd Description The maximum directory read temperature before Ceph splits a directory fragment. Type Float Default 25000 mds_bal_split_wr Description The maximum directory write temperature before Ceph splits a directory fragment. Type Float Default 10000 mds_bal_split_bits Description The number of bits by which to split a directory fragment. Type 32-bit Integer Default 3 mds_bal_merge_size Description The minimum directory size before Ceph tries to merge adjacent directory fragments. Type 32-bit Integer Default 50 mds_bal_merge_rd Description The minimum read temperature before Ceph merges adjacent directory fragments. Type Float Default 1000 mds_bal_merge_wr Description The minimum write temperature before Ceph merges adjacent directory fragments. Type Float Default 1000 mds_bal_interval Description The frequency, in seconds, of workload exchanges between MDS nodes. Type 32-bit Integer Default 10 mds_bal_fragment_interval Description The frequency, in seconds, of adjusting directory fragmentation. Type 32-bit Integer Default 5 mds_bal_idle_threshold Description The minimum temperature before Ceph migrates a subtree back to its parent. Type Float Default 0 mds_bal_max Description The number of iterations to run balancer before Ceph stops. For testing purposes only. Type 32-bit Integer Default -1 mds_bal_max_until Description The number of seconds to run balancer before Ceph stops. For testing purposes only. Type 32-bit Integer Default -1 mds_bal_mode Description The method for calculating MDS load: 1 = Hybrid. 2 = Request rate and latency. 3 = CPU load. Type 32-bit Integer Default 0 mds_bal_min_rebalance Description The minimum subtree temperature before Ceph migrates. Type Float Default 0.1 mds_bal_min_start Description The minimum subtree temperature before Ceph searches a subtree. Type Float Default 0.2 mds_bal_need_min Description The minimum fraction of target subtree size to accept. Type Float Default 0.8 mds_bal_need_max Description The maximum fraction of target subtree size to accept. Type Float Default 1.2 mds_bal_midchunk Description Ceph migrates any subtree that is larger than this fraction of the target subtree size. Type Float Default 0.3 mds_bal_minchunk Description Ceph ignores any subtree that is smaller than this fraction of the target subtree size. Type Float Default 0.001 mds_bal_target_removal_min Description The minimum number of balancer iterations before Ceph removes an old MDS target from the MDS map. Type 32-bit Integer Default 5 mds_bal_target_removal_max Description The maximum number of balancer iterations before Ceph removes an old MDS target from the MDS map. Type 32-bit Integer Default 10 mds_replay_interval Description The journal poll interval when in standby-replay mode for a hot standby . Type Float Default 1 mds_shutdown_check Description The interval for polling the cache during MDS shutdown. Type 32-bit Integer Default 0 mds_thrash_exports Description Ceph randomly exports subtrees between nodes. For testing purposes only. Type 32-bit Integer Default 0 mds_thrash_fragments Description Ceph randomly fragments or merges directories. Type 32-bit Integer Default 0 mds_dump_cache_on_map Description Ceph dumps the MDS cache contents to a file on each MDS map. Type Boolean Default false mds_dump_cache_after_rejoin Description Ceph dumps MDS cache contents to a file after rejoining the cache during recovery. Type Boolean Default false mds_verify_scatter Description Ceph asserts that various scatter/gather invariants are true . For developer use only. Type Boolean Default false mds_debug_scatterstat Description Ceph asserts that various recursive statistics invariants are true . For developer use only. Type Boolean Default false mds_debug_frag Description Ceph verifies directory fragmentation invariants when convenient. For developer use only. Type Boolean Default false mds_debug_auth_pins Description The debug authentication pin invariants. For developer use only. Type Boolean Default false mds_debug_subtrees Description Debugging subtree invariants. For developer use only. Type Boolean Default false mds_kill_mdstable_at Description Ceph injects a MDS failure in a MDS Table code. For developer use only. Type 32-bit Integer Default 0 mds_kill_export_at Description Ceph injects a MDS failure in the subtree export code. For developer use only. Type 32-bit Integer Default 0 mds_kill_import_at Description Ceph injects a MDS failure in the subtree import code. For developer use only. Type 32-bit Integer Default 0 mds_kill_link_at Description Ceph injects a MDS failure in a hard link code. For developer use only. Type 32-bit Integer Default 0 mds_kill_rename_at Description Ceph injects a MDS failure in the rename code. For developer use only. Type 32-bit Integer Default 0 mds_wipe_sessions Description Ceph deletes all client sessions on startup. For testing purposes only. Type Boolean Default 0 mds_wipe_ino_prealloc Description Ceph deletes inode preallocation metadata on startup. For testing purposes only. Type Boolean Default 0 mds_skip_ino Description The number of inode numbers to skip on startup. For testing purposes only. Type 32-bit Integer Default 0 mds_standby_for_name Description The MDS daemon is a standby for another MDS daemon of the name specified in this setting. Type String Default N/A mds_standby_for_rank Description An instance of the MDS daemon is a standby for another MDS daemon instance of this rank. Type 32-bit Integer Default -1 mds_standby_replay Description Determines whether the MDS daemon polls and replays the log of an active MDS when used as a hot standby . Type Boolean Default false

Commands: