User's Manual

hp StorageWorks File System Extender User Guide 95
Over time, the situation can arise where a large proportion of space on FSE media is occupied by old,
obsolete generations of files. FSE enables you to reclaim media space by reorganizing the data on the
media. The media reorganization process frees space on media by preserving only selected file
generations and removing the others. FSE media space can then be reused for newly migrated data.
Media reorganization is a medium-volume-based process. This means that the smallest unit of the
secondary storage space that can be reorganized is a single FSE medium volume. Similarly, the smallest
unit that can be reused is an FSE medium volume. As system volumes do not contain file data, only data
volumes can be reorganized.
Prerequisites
• Before scanning media as part of the media reorganization process run the FSC vs. media check with
the --autocorrect and --match-media options. For more information, see ”Consistency check of
FSC vs. FSE media” on page 143.
Limitation
• After the reorganization of one or more FSE medium volumes on an FSE medium, any duplicates of the
medium created before the reorganization are rendered useless, as (part of) the source medium has
been reinitialized at the end of the reorganization job.
To restore data safety level, you need to duplicate each medium that contains reorganized medium
volumes and whose sources for the reorganization process were duplicated before the reorganization.
The media reorganization process
The media reorganization process consists of two steps: scanning and copying. Each step is controlled and
performed by its own FSE job.
The scanning step is run for all FSE media in all FSE media pools that are assigned to a specified FSE
partition. This step determines the locations of valid and obsolete data on the already closed (full) and still
open FSE medium volumes, according to parameters that you define. It then records the scan results to the
Resource Management Database (RMDB). The scanning process is performed as a search through the
corresponding File System Catalog (FSC), therefore the FSE media themselves are not physically scanned.
The results of the scanning step are used in the copying step. This step copies all selected file generations
from the medium volumes being reorganized to open and empty medium volumes in the same FSE media
pool. The original volumes are then recycled and finally reinitialized. To reduce the number of drive load
and unload operations during the copying step, the data is copied to (open or empty) medium volumes on
the same medium, if any exist.
Note that the copying step of the reorganization process is not started until the scanning step has
completed, and vice versa.
Before running the copying step, you can preview the results of the scan to decide which FSE medium
volumes or FSE media you actually want to reorganize. It is only useful to reorganize volumes with a high
enough proportion of obsolete data (that is, a high enough percentage of FSE slack space).
During execution of the reorganization process, FSE progressively shows status indicators (such as
“scanned”, “in reorg”, and “recycled”) to the medium volumes being reorganized. These indicators help
you detect and track the reorganization progress for a particular medium volume. You can display these
status indicators at any time with the following command:
fsemedium --list [Barcode] --volume