Deduplication Issues - HP 12000 User Manual

6. Manually recreate the storage pools associated with the new library using the information
written down at the beginning of this procedure.
The virtual tapes that were moved into the firesafe will automatically return to their previous
locations.

Deduplication Issues

Symptom
The VLS is not deduplicating the
backup jobs.
The deduplication compression ratio
is low.
The deduplication compression ratio
was fine, but suddenly went down
significantly.
The restore performance is degrading.
Possible causes
The VLS does not free up storage on
a cartridge until:
At least two full backups of the
same policy exist on different
cartridges
The delta-differencer has processed
all of the backup sets on the
cartridge
The cartridge is physically full
The compression ratio depends on the
amount of data changed between the
backup sets. In addition, not all data
is deduplicated. For example, files less
than 32 KB in size and backup sets
less than 1 MB are ignored. If your
data sets do not change significantly
between backups, or if they contain
many small files, the compression ratio
may be low. This is expected behavior
and does not indicate a problem.
After 50 versions of a backup set have
been deduplicated, the VLS
automatically restarts the deduplication
process as though starting from
scratch. As a result, the compression
ratio will drop.
The restore performance will continue
to degrade as you restore older and
older versions of a backup.
Solution
Consider using cartridges that are
smaller than the sum of your daily
backup jobs so the cartridges
deduplicate sooner.
None
In time, the ratio will improve as more
backup sets are deduplicated.
After 50 versions of a backup set have
been deduplicated, the VLS
automatically restarts the deduplication
process as though from scratch. The
restore performance will then improve
because the restore versions are more
recent.
Deduplication Issues 177