Quantum DXi8500, User Manual

Page: 40 / 520

Chapter 1: DXi8500 System Description
Space Reclamation
10 Quantum DXi8500 User’s Guide
Space Reclamation
The space reclamation process performs multiple functions on the
DXi8500.
When data is deduplicated it is stored in a blockpool—a pool of all
unique data blocks that were captured during the data deduplication
cycle. When subsequent backup jobs occur, the data deduplication
engine searches for new data entering the DXi and uses a variable
length compression algorithm to compare new data to existing data in
the blockpool. Unique blocks are added to the blockpool and known
blocks are indexed.
The space reclamation function searches the blockpool for data blocks
that are not referenced by any pointers (that is, the files associated with
the block have been expired and removed). Once such a data block is
identified, the block is removed to make the space reusable.
For correct system operation, space reclamation
must
be run at regular
intervals (at least once a week). Quantum recommends creating a
schedule to automatically run space reclamation (see Scheduling Space
Reclamation on page 362).
It may be beneficial to schedule space reclamation for a time when
other operations are not normally being carried out. Therefore it is
important to know when to schedule the space reclamation process. As
best practice it is recommended that this process commences at least
two hours after your backup job has completed on a daily basis. It is far
more efficient to process a day’s worth of new data than a week’s
worth.
Remote Replication
Today most backup occurs on isolated devices, making it difficult to
deploy disk backup when disaster recovery protection is required. DXi-
Series solutions use data deduplication and replication to decrease by
up to 50 times the bandwidth required to move backup data over
networks and between sites. This dramatic gain makes it practical and
cost-effective for users to replicate backup data over WANs for secure,