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MDS Config Reference¶

mds_cache_memory_limit

Description: The memory limit the MDS should enforce for its cache.
Type: 64-bit Integer Unsigned
Default: 4G

mds_cache_reservation

Description: The cache reservation (memory or inodes) for the MDS cache to maintain. Once the MDS begins dipping into its reservation, it will recall client state until its cache size shrinks to restore the reservation.
Type: Float
Default: 0.05

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 is dirty 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 it into smaller transactions (MB).
Type: 32-bit Integer
Default: 10

mds_dir_max_entries

Description: The maximum number of entries before any new entries are rejected with ENOSPC.
Type: 64-bit Integer Unsigned
Default: 0

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_blocklist_interval

Description: The blocklist duration for failed MDSs in the OSD map. Note, this controls how long failed MDS daemons will stay in the OSDMap blocklist. It has no effect on how long something is blocklisted when the administrator blocklists it manually. For example, ceph osd blocklist add will still use the default blocklist time.
Type: Float
Default: 24.0*60.0

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 stats up the tree.
Type: Float
Default: 1

mds_scatter_nudge_interval

Description: How quickly dirstat changes 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 should allow clients to see request results before they commit to the journal.
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 (i.e., rjenkins)

mds_log_skip_corrupt_events

Description: Determines whether the MDS should try to skip corrupt journal events during journal replay.
Type: Boolean
Default: false

mds_log_max_events

Description: The maximum events in the journal before we initiate trimming. Set to -1 to disable limits.
Type: 32-bit Integer
Default: -1

mds_log_max_segments

Description: The maximum number of segments (objects) in the journal before we initiate trimming. Set to -1 to disable limits.
Type: 32-bit Integer
Default: 128

mds_bal_sample_interval

Description: Determines how frequently to sample directory temperature (for 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_split_size

Description: The maximum directory size before the MDS will split a directory fragment into smaller bits.
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_interval

Description: The frequency (in seconds) of workload exchanges between MDSs.
Type: 32-bit Integer
Default: 10

mds_bal_fragment_interval

Description: The delay (in seconds) between a fragment being eligible for split or merge and executing the fragmentation change.
Type: 32-bit Integer
Default: 5

mds_bal_fragment_fast_factor

Description: The ratio by which frags may exceed the split size before a split is executed immediately (skipping the fragment interval)
Type: Float
Default: 1.5

mds_bal_fragment_size_max

Description: The maximum size of a fragment before any new entries are rejected with ENOSPC.
Type: 32-bit Integer
Default: 100000

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. (used 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. (used for testing purposes only)
Type: 32-bit Integer
Default: -1

mds_bal_mode

Description

The method for calculating MDS load.

0 = Hybrid.
1 = Request rate and latency.
2 = 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 will migrate any subtree that is larger than this fraction of the target subtree size.
Type: Float
Default: 0.3

mds_bal_minchunk

Description: Ceph will ignore 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. (“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 will randomly export subtrees between nodes (testing only).
Type: 32-bit Integer
Default: 0

mds_thrash_fragments

Description: Ceph will randomly fragment or merge directories.
Type: 32-bit Integer
Default: 0

mds_dump_cache_on_map

Description: Ceph will dump the MDS cache contents to a file on each MDSMap.
Type: Boolean
Default: false

mds_dump_cache_after_rejoin

Description: Ceph will dump MDS cache contents to a file after rejoining the cache (during recovery).
Type: Boolean
Default: false

mds_verify_scatter

Description: Ceph will assert that various scatter/gather invariants are true (developers only).
Type: Boolean
Default: false

mds_debug_scatterstat

Description: Ceph will assert that various recursive stat invariants are true (for developers only).
Type: Boolean
Default: false

mds_debug_frag

Description: Ceph will verify directory fragmentation invariants when convenient (developers only).
Type: Boolean
Default: false

mds_debug_auth_pins

Description: The debug auth pin invariants (for developers only).
Type: Boolean
Default: false

mds_debug_subtrees

Description: The debug subtree invariants (for developers only).
Type: Boolean
Default: false

mds_kill_mdstable_at

Description: Ceph will inject MDS failure in MDSTable code (for developers only).
Type: 32-bit Integer
Default: 0

mds_kill_export_at

Description: Ceph will inject MDS failure in the subtree export code (for developers only).
Type: 32-bit Integer
Default: 0

mds_kill_import_at

Description: Ceph will inject MDS failure in the subtree import code (for developers only).
Type: 32-bit Integer
Default: 0

mds_kill_link_at

Description: Ceph will inject MDS failure in hard link code (for developers only).
Type: 32-bit Integer
Default: 0

mds_kill_rename_at

Description: Ceph will inject MDS failure in the rename code (for developers only).
Type: 32-bit Integer
Default: 0

mds_inject_skip_replaying_inotable

Description: Ceph will skip replaying the inotable when replaying the journal, and the premary MDS will crash, while the replacing MDS won’t. (for developers only).
Type: Boolean
Default: false

mds_kill_skip_replaying_inotable

Description: Ceph will skip replaying the inotable when replaying the journal, and the premary MDS will crash, while the replacing MDS won’t. (for developers only).
Type: Boolean
Default: false

mds_wipe_sessions

Description: Ceph will delete all client sessions on startup (for testing only).
Type: Boolean
Default: false

mds_wipe_ino_prealloc

Description: Ceph will delete ino preallocation metadata on startup (for testing only).
Type: Boolean
Default: false

mds_skip_ino

Description: The number of inode numbers to skip on startup (for testing only).
Type: 32-bit Integer
Default: 0

mds_min_caps_per_client

Description: Set the minimum number of capabilities a client may hold.
Type: Integer
Default: 100

mds_max_ratio_caps_per_client

Description: Set the maximum ratio of current caps that may be recalled during MDS cache pressure.
Type: Float
Default: 0.8