HP 12000 HP 12200 Gateway Virtual Library System User Guide (BW403-10001, June - Page 177

Deduplication Issues, written down at the beginning of this procedure.

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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. Possible causes Solution The VLS does not free up storage on a cartridge until: • At least two full backups of the same policy exist on different cartridges Consider using cartridges that are smaller than the sum of your daily backup jobs so the cartridges deduplicate sooner. • The delta-differencer has processed all of the backup sets on the cartridge • The cartridge is physically full The deduplication compression ratio is low. The compression ratio depends on the None 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. The deduplication compression ratio was fine, but suddenly went down significantly. After 50 versions of a backup set have In time, the ratio will improve as more been deduplicated, the VLS backup sets are deduplicated. automatically restarts the deduplication process as though starting from scratch. As a result, the compression ratio will drop. The restore performance is degrading. The restore performance will continue to degrade as you restore older and older versions of a backup. 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

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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
Solution
Possible causes
Symptom
Consider using cartridges that are
smaller than the sum of your daily
The VLS does not free up storage on
a cartridge until:
The VLS is not deduplicating the
backup jobs.
backup jobs so the cartridges
deduplicate sooner.
•
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
None
The compression ratio depends on the
amount of data changed between the
The deduplication compression ratio
is low.
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.
In time, the ratio will improve as more
backup sets are deduplicated.
After 50 versions of a backup set have
been deduplicated, the VLS
The deduplication compression ratio
was fine, but suddenly went down
significantly.
automatically restarts the deduplication
process as though starting from
scratch. As a result, the compression
ratio will drop.
After 50 versions of a backup set have
been deduplicated, the VLS
The restore performance will continue
to degrade as you restore older and
older versions of a backup.
The restore performance is degrading.
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