User's Manual

148 Migration, release, recall, and deletion
Sequential copying
The number of configured FSE media pools determines the number of data copies for the corresponding
FSE partition; if you have only one drive configured in FSE or if your FSE partition can use a maximum of
one drive for migration at a time (MaxNumDrivesMigration variable in the FSE partition configuration
file), your copies will be done sequentially. Also, if there are not enough free drives available during the
migration job, copies that could not be made in parallel will be made sequentially. Note that a media pool
cannot be assigned to multiple partitions.
Once a job is started it must be finished as soon as possible to free storage space in the FSE disk buffer.
The job priority increases over time to ensure that the job will allocate enough resources - drives and media
- to complete. If some copies have already been made while others still need to be made and another job
with a higher job priority was triggered in between, the priority of the migration job is recalculated
(increased) using a special factor (PhaseFactor variable in the FSE system configuration file). Such
handling gives the job a high enough priority to allocate the required resources as soon as possible.
TIP: To avoid situations, when migrations performing sequential copying would exhaust storage space of
the FSE disk buffer, extend the FSE disk buffer with additional file systems or volumes. For details, see
chapter ”Monitoring and maintaining FSE”, section ”Extending storage space of FSE disk buffer” on
page 176.
HSM file system access modes
Normally, data on HSM file systems is only available when FSE processes are running, that is, when the
FSE system is in a fully operational state. In certain situations, however, you may need access to the data
even though the FSE implementation cannot be started for some reason. The Limited Access Mode (LAM)
feature of the FSE implementation allows this by enabling read-only access to directories and files on the
mounted HSM file system. While in the read-only mode, the HSM file system is not controlled by
Hierarchical Storage Manager.
NOTE: Limited Access Mode is available on supported Windows operating systems.
On Windows systems, LAM is available with full functionality, including the ability to manually switch
between LAM and FAM and vice versa.
Limited Access Mode (LAM) and Full Access Mode (FAM)
A properly configured HSM file system on a Windows FSE client, from which NTFS has been detached
using the fse --dismount-ntfs command can be mounted implicitly or explicitly. The implicit mount is
triggered automatically after an object on the HSM file system is accessed for the first time. The explicit
mount is executed manually invoking the fse --mount command for the corresponding disk volume,
and can be performed only while FSE processes are running.
Once mounted, each HSM file system remains mounted all the time, even after the FSE client host is
restarted. A mounted HSM file system, however, can operate in Limited Access Mode (LAM) or Full Access
Mode (FAM). The operational mode depends on whether the FSE processes are running and whether an
FSE administrator decided to switch between the two modes manually.
An HSM file system operates in LAM:
• before the FSE implementation has been started
• after the FSE implementation has been shut down
• while the FSE implementation is fully operational, after the FSE administrator has manually switched
from FAM to LAM using the FSE command-line interface.
An HSM file system operates in FAM:
• after the FSE implementation has been started