User's Manual

114 Migration, release, recall, and deletion
The period of time since the first file was put on the list is greater than MaxWaitTime.
• Situation 3
There are at least MaxNumMigFiles on the list.
• Situation 4
The total size of files to be migrated is equal or greater than MaxMigSize.
Default migration policy
Default migration policy is defined in the FSE configuration template for FSE partition configuration. For
details, see ”Template for FSE partitions - Migration part” on page 248.
Release
In contrast to migration policy, the most important release policy parameters are watermarks. The
watermark parameter values define when the release process is triggered. You define configuration
parameters relevant for your release policy in the FSE partition configuration file. You should check the
default watermark parameters for your release policy and adjust the settings according to your
environment.
You can also exclude specified files from the release process. This allows you to specify files or sets of files
which should be skipped during a release operation so that they remain permanently online. Exclusion
from release is described in ”Exclusion from release” on page 116.
Watermarks
FSE prevents HSM file systems from becoming full using special parameters called watermarks. They are
based on a simple principle of defining the value for the normal, high, and critical occupation of disk
space. Watermark parameters are the trigger for releasing the file data from the file system.
Typically, when the HSM file system volume reaches a certain percentage (defined with a watermark), all
files that meet defined criteria are released from the disk. This results in freeing up capacity on disk systems
thus providing space for new files and files that will be recalled.
For each configured FSE partition, three watermarks are defined in the FSE partition configuration file: low,
high, and critical. Their values must follow the rule low watermark < high watermark < critical watermark.
Critical watermark
When this watermark is reached, the forced release job is started. All files that are on the release
candidate list are released, regardless of other conditions—retention times and minimum file size are not
checked. The release job is stopped when the high watermark on the HSM file system is reached. Files not
released during the release job remain on the release list.