User's Manual

186 Backup, restore, and recovery
Recovery
FSE provides functionality for recovering from disasters that can happen to the FSE implementation, and
which can be used as an alternative or as a supplement to the conventional FSE restore process. HSM file
systems and File System Catalogs (FSCs) can be restored using specially tailored recovery methods.
If one or more HSM file systems are damaged, you can use HSM file system recovery to recreate an HSM
file system from the Name Space Catalogs, as an alternative to FSE backup and restore.
File System Catalog (FSC) recovery is designed for recreation of the damaged or missing FSC files from the
Fast Recovery Information (FRI) data and the data migrated to FSE media. It can also be used in less severe
situations, for example when entries in the FSC are inconsistent with the corresponding HSM file system.
See the recommended ways of using FSE backup and restore and FSE recovery in ”Defining your backup
strategy” on page 171.
File System Catalog recovery
The File System Catalog is recreated either from Fast Recovery Information (FRI), if it is available, or from
the migrated metadata.
NOTE: During an FSC recovery, media reorganization is inhibited.
Note that the results of a previously implemented reorganisation scan are invalidated by an FSC recovery.
To perform FSC recovery, proceed as follows:
1. Disable the FSE partition.
2. Remove the FSC directory.
3. Enable the FSE partition.
4. Start the recovery of FSC:
For example, to start recovery of the File System Catalog for FSE partition fse_fs01 enter:
When running the fserecover --fsc command the following occurs:
1. If FRI is located on disk, which is the case for all data volumes that are not yet full, recovery is done
from these temporary FRI files.
2. If a data volume on a partitioned FSE medium is full and its FRI has been written to the system volume
on the medium, the recovery is done from FRI on the system volume. This is the fastest method since all
FRI is located on the system volume.
3. If an FSE medium is not partitioned to have a system volume, the recovery is done from FRI on the data
volume, since each data volume includes its own FRI.
The FRI on the data volume is also used if the FRI on the system volume is invalid.
4. If FRI is not available, the recovery process needs to recreate it from file data on the data volume. This
is a time-consuming process since all data need to be read first, and only then can FRI be recreated
and used to recover FSC.
Once FSC recovery is completed, you should run the FSC consistency check as described in ”Consistency
check of FSC vs. HSM file system” on page 141.
HSM file system recovery
An HSM file system is recovered directly from the Name Space Catalog (NSC), which is a part of the File
System Catalog. Since the Name Space Catalog contains complete file system structure data (such as the
directory structure, file attributes, and security), the HSM file system structure can be recreated according to
this information.
fserecover --fsc PartitionName
fserecover --fsc fse_fs01