File placement

SAN File System provides automatic file placement at the time of creation through the use of policies and storage pools. You can create quality-of-service storage pools that are available to all users and define rules and policies that place newly created files into the appropriate storage pool automatically.

The file-placement policy tells a metadata server where to place the data for a newly created file in a specific storage pool if the attributes of that file meet the criteria specified in a rule. A rule can apply to any file being created or to only files being created within a specific fileset depending on how it is defined. Other criteria include these:

The rules in a file-placement policy are evaluated in order until the condition in one of the rules is met. The data for the file is then stored in the storage pool that is specified by the applicable rule. If none of the conditions specified in the rules is met, the data for the file is stored in the default storage pool.

Rules in a policy are evaluated only when a file is being created. If you switch from one policy to another, the rules in the new policy apply only to newly created files. Activating a new policy does not change the storage pool assignments for existing files. Moving a file does not cause a policy to be applied. You can create multiple policies, but only one policy can be active at a time.

After a file has been created, you can check its storage pool assignment using the statfile command from the administrative command-line interface (CLI). You can also use the statpolicy command from the administrative CLI to view the statistics about the file-placement policy rules.

Attention:
It is recommended that you do not use creation time, user ID or group ID to place file. If you do base any file-placement rules on creation time, user IDs, or group IDs, be aware of these restore and migration considerations:
  • A rule that uses the creation date as the placement criteria assigns a file based on the time that the file was restored or migrated, not the original creation time.
  • A rule that uses a user ID or group ID as the placement criteria assigns a file based on the effective user and group IDs of the restore process, not the original file's user and group IDs.

Parent topic: Storage management

Related concepts
Storage pools

Related tasks
Activating a policy
Creating a policy
Creating a storage pool
Changing the rules in a policy

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