Defining external pools

When you define external pools, follow these rules.

GPFS file management policy rules control data migration into external storage pools. Before you write a migration policy, you must define the external storage pool that the policy reference. After you define the storage pool, you can then create policies that set thresholds that trigger data migration into or out of the referenced external pool.

When a storage pool reaches the defined threshold or when you invoke mmapplypolicy, GPFS processes the metadata, generates a list of files, and invokes a user provided script or program which initiates the appropriate commands for the external data management application to process the files. This allows GPFS to transparently control offline storage and provide a tiered storage solution that includes tape or other media.

Before you migrate data to an external storage pool, you must define that pool. To define external storage pools, use a GPFS policy rule as follows:
RULE EXTERNAL POOL 'PoolName' EXEC 'InterfaceScript' [OPTS 'OptionsString'] [ESCAPE 'SpecialCharacters']
Where:
  • PoolName defines the name of the storage pool
  • InterfaceScript defines the program or script to be invoked to migrate data to or from the external pool
  • OptionsString is an optional string that, if provided, will be passed to the InterfaceScript
You must have a separate EXTERNAL POOL rule for each external pool that you wish to define.

Example of a rule that defines a storage pool

The following rule defines a storage pool called externalpoolA.
RULE EXTERNAL POOL 'externalpoolA' EXEC '/usr/hsm/bin/hsmControl' OPTS '-server=hsm-manager.nyc.com'
In this example:
  • externalpoolA is the name of the external pool
  • /usr/hsm/bin/hsmControl is the location of the executable script that will be invoked when there are files for migration
  • -server=hsm-manager.nyc.com is the location of storage pool externalpoolA

For more information, refer to User-provided program for managing external pools.