Appendix B. Metadata Server daemon configuration Reference

Refer the list commands that can be used for 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 to use this parameter instead of the mds cache size parameter.
Type
64-bit Integer Unsigned
Default
1073741824
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 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 before Ceph breaks the directory into smaller transactions, in MB.
Type
32-bit Integer
Default
90
mds_decay_halflife
Description
The half-life of 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 an MDS laggy, and possibly replace 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 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 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 MDS failure in MDS Table code. For developer use only.
Type
32-bit Integer
Default
0
mds_kill_export_at
Description
Ceph injects MDS failure in the subtree export code. For developer use only.
Type
32-bit Integer
Default
0
mds_kill_import_at
Description
Ceph injects MDS failure in the subtree import code. For developer use only.
Type
32-bit Integer
Default
0
mds_kill_link_at
Description
Ceph injects MDS failure in hard link code. For developer use only.
Type
32-bit Integer
Default
0
mds_kill_rename_at
Description
Ceph injects 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 deletea 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