NDB Cluster Disk Data Tables Important 23.5.10 NDB Cluster Disk Data Tables 23.5.10.1 NDB Cluster Disk Data Objects To participate in an NDB Cluster, the  mysqld  process must be started with  both the options  --ndbcluster  and  --ndb-connectstring  (or their equivalents in my.cnf ). If  mysqld  is started with only the  --ndbcluster  option, or if it is unable to contact the cluster, it is not possible to work with  NDB  tables,  nor is it possible to create any new tables regardless of storage engine . The latter restriction is a safety measure intended to prevent the creation of tables having the same names as  NDB tables while the SQL node is not connected to the cluster. If you wish to create tables using a different storage engine while the  mysqld  process is not participating in an NDB Cluster, you must restart the server  without  the  --ndbcluster  option. NDB Cluster supports storing nonindexed columns of  NDB  tables on disk, rather than in RAM. Column data and logging metadata are kept in data files and undo log files, conceptualized as tablespaces and log file groups, as described in the next section—see Section 23.5.10.1, “NDB Cluster Disk Data Objects” . NDB Cluster Disk Data performance can be influenced by a number of configuration parameters. For information about these parameters and their effects, see Disk Data Configuration Parameters, and Disk Data and GCP Stop errors. Beginning with NDB 8.0.19, you should also set the  DiskDataUsingSameDisk  data node configuration parameter to  false  when using separate disks for Disk Data files. See also Disk Data file system parameters. NDB 8.0.19 (and later) provides improved support when using Disk Data tables with solid-state drives, in particular those using NVMe. See the following documentation for more information: NDB Cluster Disk Data storage is implemented using the following objects: Undo log files and data files are actual files in the file system of each data node; by default they are placed in  ndb_ node_id _fs  in the  DataDir  specified in the NDB Cluster  config.ini  file, and where  node_id is the data node’s node ID. It is possible to place these elsewhere by specifying either an absolute or relative path as part of the filename when creating the undo log or data file. Statements that create these files are shown later in this section. • Tablespace : Acts as containers for other Disk Data objects. A tablespace contains one or more data files and one or more undo log file groups. • Data file : Stores column data. A data file is assigned directly to a tablespace. • Undo log file : Contains undo information required for rolling back transactions. Assigned to an undo log file group. • log file group : Contains one or more undo log files. Assigned to a tablespace. 4498 •Section 23.5.14.40, “The ndbinfo pgman_time_track_stats Table” •Section 23.5.14.29, “The ndbinfo diskstats_1sec Table” •Section 23.5.14.28, “The ndbinfo diskstat Table” •Disk Data latency parameters