Settings that control the space usage of a file system

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You can control the space usage of a file system by indicating how and when files are migrated and recalled.

You can control the following aspects of file migration and recall on a file system:

  • The high and low thresholds for your file system that determine when threshold migration automatically starts and stops
  • The total number of megabytes of data that you can migrate and premigrate from your file system to IBM Storage® Protect storage
  • The file size before it is migrated
  • The size of the stub files that remain on your local file system when you migrate your files
  • The order in which eligible files automatically migrate from your local file system
  • The amount of free space the space management client maintains on your local file system
  • The minimum size (in megabytes) for a file to qualify for partial file recall
  • The minimum size (in megabytes) for a file to qualify for streaming recall mode
  • The maximum number of files in the space-managed file system.

The information for each file system is stored in the hsmfsconfig.xml file, which is in the appropriate .SpaceMan directory. You can modify the settings in the hsmfsconfig.xml file with the dsmmigfs update command. You can also use the dsmmigfs query command to display the settings in this file.

At any time after you add space management to your local file systems, you can update the settings, if necessary.

Copy several files into your migrated file system after you add space management and run the dsmmigrate command. If you are running open registration, the command prompts you for your node password and contact information the first time that you run it.

You can increase file transfer performance by allowing failover of automatic migration and recall capabilities to source nodes within a cluster environment.

Changes to space management settings take effect in the following manner:

  • If you change the high and low thresholds or the premigration percentages for a file system, the new values take effect immediately.
  • If you change the stub file sizes, the new values take effect only for files that are migrated after you change the settings.
  • If you reduce the quota, and the data that you currently migrate exceeds the new quota, any additional files from your file system do not migrate. Sufficient files must be recalled during automatic or selective recall to drop the total number of megabytes of migrated and premigrated data below the new quota.
  • If you change the maximum number of files and sufficient space is available, the current complete file index (CFI) is replaced by the newly sized CFI. Sufficient space is determined by the available free space plus the size of the current CFI. If the new value of the maxfiles parameter of the dsmmigfs command is 0, then the CFI is sized to the maximum required space in the file system. If the value of the maxfiles parameter is smaller than the actual number of files in the file system, or greater than the theoretical limit, then the CFI is sized to the theoretical limit for the file system.

On IBM® Storage Scale file systems, you can use the IBM Storage Scale policy engine to monitor space thresholds and search for migration candidates.

For information about configuring IBM Storage Scale integration with the space management client, see Technote 7018848.