User's Manual

126 Migration, release, recall, and deletion
The following graphic shows file-status changes, including transitions of file entries between FSE HSM lists.
The MinFileAge parameter is one of the configuration parameters for an FSE partition. It represents the
period of time during which a file must be left intact to become a migration candidate.
Figure 25 Changes of states of files under FSE
Example scenario of migration and release
This example presents how the configured migration and release policies affect everyday work of FSE
users.
1. An FSE user created a new file and saved it with a name myfile.doc. He then continued working on
the file and updating it. Hierarchical Storage Manager (HSM) noticed the change and added
myfile.doc to the dirty file list.
2. The user finished working on myfile.doc and closed it. After 10 minutes, the file was moved from
the dirty file list to the migration candidate list.
The time interval of 10 minutes is defined by the parameter MinFileAge in the migration policy. It
represents a period between the moment of the last file change and the moment when the file is put on
the migration candidate list.
3. After 20 minutes myfile.doc was migrated to media, and moved from migration candidate list to the
release candidate list.
The time interval of 20 minutes is defined by the parameter MaxWaitTime in the migration policy. It
represents the maximum period of time between the moment when the first file is added to an empty
migration candidate list and the moment when migration of files on the migration candidate list is
started.
4. After the used capacity of the HSM file system exceeded 85%, HSM triggered a corresponding release
process. myfile.doc was released together with other files on the release candidate list. Its status
was set to offline.
The percentage of 85% is defined by the parameter HighWatermark in the release policy. It
represents the percentage of used disk space on an HSM file system that triggers a release job.
Policies
FSE control over the files in use is based on user-defined policies. These are rules by which migration,
release, and deletion jobs are executed. Each process requires its own policy, thus migration policy,
release policy, and deletion policy. Each FSE partition has its own set of policies.
Different policies can be defined for individual FSE partitions, according to the partition’s purpose and the
way it is used. Policies are defined in FSE partition configuration files as a series of parameters. These are
read and used by the Hierarchical Storage Manager and the Partition Manager at startup (migration and