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System Description
Space Reclamation
The space reclamation process performs multiple functions on the ETERNUS CS800.
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 ETERNUS CS800 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 refer-
enced 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. Therefore it is important to know when to schedule the space
reclamation process. By default the process will commence daily at 01:00 pm. As best
practice it is recommended that this process commences 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. The ETERNUS CS800 solution uses data
deduplication and replication to decrease 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, network-based disaster recovery
protection, and it lets users combine rapid, local restores with sound disaster recovery
protection.
With ETERNUS CS800 replication, users can transmit data from a single site or multiple
sites to a central location using any ETERNUS CS800. The replication is an asynchronous,
automated background process that includes encryption of data in transit. This model for
protecting the distributed enterprise allows users to combine disk storage, remote repli-
cation and tape backup for an optimal combination of performance, simplicity and security.
For more information on implementing a replication plan, see Chapter
page
341.
U41840-J-Z125-7-76
Space Reclamation
"Replication" on
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