Quantum DXi4510, User Manual

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Chapter 1: DXi4000 System Description
Space Reclamation
6 Quantum DXi4000 User’s Guide
Compression
The DXi4000 systems use compression technology after duplicate blocks
have been identified and replaced as part of the deduplication process.
With compression, unique data that has been through the data
deduplication process can be compressed at a typical ratio of
approximately 2:1. This enables you to maximize the storage capacity of
your system.
Space Reclamation
The space reclamation process performs multiple functions on the
DXi4000.
When data is deduplicated it is stored in a block pool—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 block pool. Unique blocks are added to the block pool 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.
It may be beneficial to schedule space reclamation for a time when
other operations are not normally being carried out. By default the
process will commence every Sunday at 1:00pm. However, to maximize
performance and capacity utilization, it is highly recommended that this
process is performed on a daily basis. 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.