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6.1.1.2. Cluster Data Node FileSystemDir Files

This directory is named ndb_nodeid_fs, where nodeid is the data node's node ID. It contains the following files and directories:

Files:

  • data-nodeid.dat

  • undo-nodeid.dat

Directories:

  • LCP: In MySQL Cluster NDB 6.3.8 and later MySQL Cluster releases, this directory holds 2 subdirectories, named 0 and 1, each of which which contain locals checkpoint data files, one per local checkpoint (see Configuring MySQL Cluster Parameters for Local Checkpoints).

    Prior to MySQL Cluster NDB 6.3.8, this directory contained 3 subdirectories, named 0, 1, and 2, due to the fact that NDB saved 3 local checkpoints to disk (rather than 2) in these earlier versions of MySQL Cluster.

    These subdirectories each contain a number of files whose names follow the pattern TNFM.Data, where N is a table ID and and M is a fragment number. Each data node typically has one primary fragment and one backup fragment. This means that, for a MySQL Cluster having 2 data nodes, and with NoOfReplicas equal to 2, M is either 0 to 1. For a 4-node cluster with NoOfReplicas equal to 2, M is either 0 or 2 on node group 1, and either 1 or 3 on node group 2.

    In MySQL Cluster NDB 7.0 and later, when using ndbmtd there may be more than one primary fragment per node. In this case, M is a number in the range of 0 to the number of LQH worker threads in the entire cluster, less 1. The number of fragments on each data node is equal to the number of LQH on that node times NoOfReplicas.

    Note

    Increasing MaxNoOfExecutionThreads does not change the number of fragments used by existing tables; only newly-created tables automatically use the new fragment count. To force the new fragment count to be used by an existing table after increasing MaxNoOfExecutionThreads, you must perform an ALTER TABLE ... REORGANIZE PARTITION statement (just as when adding new node groups in MySQL Cluster NDB 7.0 and later).

  • Directories named D1 and D2, each of which contains 2 subdirectories:

    • DBDICT: Contains data dictionary information. This is stored in:

      • The file P0.SchemaLog

      • A set of directories T0, T1, T2, ..., each of which contains an S0.TableList file.

    • Directories named D8, D9, D10, and D11, each of which contains a directory named DBLQH.

      In each case, the DBLQH directory contains N files named S0.Fraglog, S1.FragLog, S2.FragLog, ..., SN.FragLog, where N is equal to the value of the NoOfFragmentLogFiles configuration parameter.

      The DBLQH directories also contain the redo log files.

    • DBDIH: This directory contains the file PX.sysfile, which records information such as the last GCI, restart status, and node group membership of each node; its structure is defined in storage/ndb/src/kernel/blocks/dbdih/Sysfile.hpp in the MySQL Cluster source tree. In addition, the SX.FragList files keep records of the fragments belonging to each table.

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