User's Manual

12 Introducing HP StorageWorks File System Extender
1. Files from the migration candidate list are copied from the HSM file system to a special storage space
on the FSE server, called FSE disk buffer. The FSE disk buffer location is platform-dependent.
Linux specific
The root directory of the FSE disk buffer is /var/opt/fse/diskbuf.
Windows specific
The root directory of the FSE disk buffer is %InstallPath%\var\diskbuf.
The value of %InstallPath% depends on the path selection during FSE installation. It defaults to
C:\Program Files\Hewlett-Packard\FSE.
2. Data from the FSE disk buffer is copied to FSE media. To have redundant copies of the file data made
during the migration job, the respective FSE partition must have multiple media pools assigned to it. For
more information, see ”Multiple copying” on page 147.
Once the migration job is completed, the temporary location is cleared. The file entry in the Hierarchical
Storage Manager (HSM) is moved from the migration candidate list to the release candidate list.
For further information on migration process and its configuration, see chapter ”Migration, release, recall,
and deletion” on page 123.
Release
Release is a process whose purpose is to free some space on the HSM file system. During this process, file
data is removed from the HSM file system, and only file headers are preserved. Release naturally follows
migration or recall. FSE starts a release according to watermark parameters. For more information, see
”Watermarks” on page 129.
Once the file has been migrated to FSE media, it becomes a release candidate. FSE checks the release
candidates for changes. If a file on the release candidate list was not modified, and the space usage on
the HSM file system reaches the high watermark, the content (file data) of the file is removed from the HSM
file system to free disk space. A similar event happens when the space usage on the HSM file system
reaches the critical watermark. In this case, however, all migrated files are released, regardless of how
much time has passed since their last migration.
Once the release operation is completed, the file is offline and its file entry is removed from the release
candidate list.
For further information on release process and its configuration, see ”Migration, release, recall, and
deletion” on page 123.
Recall
Recall is a process of copying file contents from FSE media back to an HSM file system. It is normally
triggered when an offline file is accessed, therefore it is the reverse process to migration.
Recall is done in two steps:
1. File content is copied from the FSE media to a special storage space on the FSE server, called FSE disk
buffer.
2. File content from the FSE disk buffer is copied back to the HSM file system, thus making the file online
again.
Once the recall job is completed, the temporary location is cleared, and the offline file changes its status to
online. Its file entry in the Hierarchical Storage Manager is added to the release candidate list. This
process is transparent to the user.
A recall is triggered automatically when an offline file is accessed on the HSM file system. However, FSE
also stores on the FSE media older versions of files, referred to as older generations. You can manually
recall a particular older generation of a file using the FSE command-line interface. For details, see
”Recalling older generations of a file” on page 160. Sometimes you may even want to have files recalled
before they are actually needed. FSE includes functionality to manually recall a single file or a set of files
from FSE media. You can perform such manual recall using the FSE command-line interface. For details on
recalling a single file, see the fsefile man page. For details on recalling a set of files, see section
”Recalling sets of files in an efficient way” on page 162.