17.5.12.2 Using Symbolic Links with Disk Data Objects

The performance of a MySQL Cluster that uses Disk Data storage can be greatly improved by separating data node file systems from undo log files and tablespace data files and placing these on different disks. In early versions of MySQL Cluster, there was no direct support for this in MySQL Cluster, but it was possible to achieve this separation using symbolic links as described in this section. MySQL Cluster NDB 7.2 supports the data node configuration parameters FileSystemPathDD, FileSystemPathDataFiles, and FileSystemPathUndoFiles, which make the use of symbolic links for this purpose unnecessary. For more information about these parameters, see Disk Data file system parameters.

Each data node in the cluster creates a file system in the directory named ndb_node_id_fs under the data node's DataDir as defined in the config.ini file. In this example, we assume that each data node host has 3 disks, aliased as /data0, /data1, and /data2, and that the cluster's config.ini includes the following:

[ndbd default]
DataDir= /data0

Our objective is to place all Disk Data log files in /data1, and all Disk Data data files in /data2, on each data node host.

Note

In this example, we assume that the cluster's data node hosts are all using Linux operating systems. For other platforms, you may need to substitute you operating system's commands for those shown here.

To accomplish this, perform the following steps: