The GPFS token system's effect on cache settings

Lock tokens play a role in maintaining cache consistency between nodes.

A token allows a node to cache data it has read from disk, because the data cannot be modified elsewhere without revoking the token first.

Note the following facts about the attributes maxFilesToCache and maxStatCache:

  • For the default values, see mmchconfig command.

    In versions of IBM Storage Scale earlier than 5.0.2, the maxStatCache attribute is not effective on the Linux® platform unless the Local Read-Only Cache (LROC) is configured. For more information, see mmchconfig command.

  • The maxStatCache attribute can be set higher on user-interactive nodes and lower on dedicated compute nodes, because ls -l performance is mostly a human response issue.
  • The maxFilesToCache attribute must be large enough to handle the number of concurrently open files and allow caching of recently used files. Note that increasing this value increases the memory that is used by IBM Storage Scale. For information about calculating the memory that is consumed by maxFilesToCache attribute, see Cache usage.
  • The attributes maxFilesToCache and maxStatCache are indirectly affected by the number of manager nodes that are defined in the cluster. Having more manager nodes typically allows more tokens to be managed by the cluster.