Minimum release level of a cluster

The minimum release level of a cluster is the currently enabled level of functionality of the cluster. It is expressed as an IBM Storage Scale version number, such as 5.1.7.

Minimum release level
Access to files in remote clusters

Minimum release level

The minimum release level is a common level of functionality that all the nodes of a cluster can participate in. For example, if the minimum release level of a cluster is 5.1.7, the nodes in the cluster can use all the features that are installed with IBM Storage Scale version 5.1.7 or earlier.

Note: The minimum release level is a cluster-level attribute. It does not apply across clusters. Each cluster has its own minimum release level.

To maintain a common level of functionality in the cluster, IBM Storage Scale does not enable installed features that require a version of IBM Storage Scale that is later than the minimum release level. For example, if some or even all of the nodes of a cluster are installed with version 5.0.2.0 of IBM Storage Scale, but the minimum release level is 5.0.0.0, nodes in the cluster cannot use installed features that require a later version of the product than 5.0.0.0. For instance, nodes in the cluster cannot use the file audit logging feature, which was introduced in 5.0.2 and requires version 5.0.2 or later. File audit logging is not enabled in the cluster until the minimum release level is raised to 5.0.2 or later.

To display the minimum release level of a cluster, issue the mmlsconfig command:

# mmlsconfig
Configuration data for cluster example.cluster:
--------------------------------------------
. . .
minReleaseLevel 5.0.0.0
. . .

When a cluster is created, the minimum release level of the cluster is set to the release level of the node where the mmcrcluster command is issued.

Tip: The results of running the mmcrcluster command depend partly on the relative release levels of the nodes that you are including in the new cluster:

If the mmcrcluster command is issued on the node with the lowest release level in the cluster, then cluster creation succeeds and the minimum release level of the cluster corresponds to the release level of the node from which the cluster was created.
If the mmcrcluster command is issued on a node other than the node with the lowest release level, then one of two outcomes can occur. Cluster creation might fail, or it might succeed but exclude nodes with lower release levels from the cluster. In either case the command might display an error message like the following one:
```
6027-1599 The level of GPFS on node vmip135.gpfs.net does not support the requested action.
```

Important: Nodes in a cluster can run different versions of IBM Storage Scale only if the versions are compatible. For more information, see the subsection "Can different IBM Storage Scale maintenance levels coexist?" in IBM Storage Scale FAQ in IBM® Documentation.

To increase the minimum release level to the latest common level of functionality, issue the following command:

mmchconfig release=LATEST

For more information, see mmchconfig command. Issuing the mmchconfig release=LATEST command is frequently one of the final steps in upgrading a cluster to a later version of IBM Storage Scale. For more information, see Completing the upgrade to a new level of IBM Storage Scale.

Warning: You cannot decrease the minimum release level of a cluster or revert it to the previous level, except by a lengthy process of uninstalling and reinstalling. For more information, see Reverting to the previous level of IBM Storage Scale.

When you raise the minimum release level by running the mmchconfig release=LATEST command, nodes that are installed with earlier versions of IBM Storage Scale cannot be added to the cluster unless they are upgraded to a version greater than or equal to the minimum release level of the cluster.

Some features of IBM Storage Scale that are available at an earlier minimum release level might work differently or not be available at a later minimum release level. Examples:

In the mmcrfs command and the mmchfs command, the default value of the -S parameter can be different depending on the minimum release level. For more information, see mmcrfs command and mmchfs command.
The default value of the CipherList parameter of the mmauth command and the cipherList parameter of the mmchconfig command can be different depending on the minimum release level. For more information, see Security mode and Completing the upgrade to a new level of IBM Storage Scale.

Access to files in remote clusters

Nodes in one cluster can mount file systems in another cluster if the following requirements are met:

The minimum release levels of the two clusters are compatible. For more information, see the Can different IBM Spectrum® Scale™ maintenance levels coexist? in IBM Storage Scale FAQ in IBM Documentation.
The version of the accessing node is greater than or equal to the file system format version of the file system being mounted.
For more information, see File system format changes between versions of IBM Storage Scale and the description of the --version parameter in mmcrfs command.