path: root/doc/cephfs/mds-config-ref.rst

======================
 MDS Config Reference
======================

``mds cache memory limit``

:Description: The memory limit the MDS should enforce for its cache.
              Administrators should use this instead of ``mds cache size``.
:Type:  64-bit Integer Unsigned
:Default: ``1073741824``

``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 size``

:Description: The number of inodes to cache. A value of 0 indicates an
              unlimited number. It is recommended to use
              ``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 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: ``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 MDSs in the OSD map. Note,
              this controls how long failed MDS daemons will stay in the
              OSDMap blacklist. It has no effect on how long something is
              blacklisted when the administrator blacklists it manually. For
              example, ``ceph osd blacklist add`` will still use the default
              blacklist 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 iteration 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 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``