D2D Replication; How It Works; D2D Replication Implementation - HP StorageWorks 12000 - Virtual Library System EVA Gateway Manual

Configuring backup rotation schemes correctly is very important to ensure the maximum efficiency of
the product by reducing the amount of housekeeping required. See
Reduce Housekeeping.

D2D Replication

The D2D replication technology (which leverages Dynamic deduplication) offers:
• Ease-of-Use. Unlike some competitors, D2D has a web based GUI to configure replication targets,
implement policies, and provide comprehensive reporting. Wizards for replication and recovery
make the configuration easy to accomplish in only five steps.
• Tape Offload functionality. Only HP offers easy migration of data from virtual tape to physical
tape either for off-site/archiving of data for compliance reasons, or for use in tape initialization
during replication setup, and in the disaster recovery process.
• HP D2D can run up to eight replications concurrently, allowing optimal use of the bandwidth
available so your replication completes as soon as possible.
• The D2D implementation offers link throttling so you can determine what percent of the available
link speed is to be utilized for replication. This prevents D2D replication swamping the inter-site
link and maintains acceptable application performance across sites whilst replication is also taking
place.
• With many-to-one and N-way replication, the D2D4100 devices can support up to 24:1 fan in
from D2D2500s located at remote sites, allowing you to make replication very cost effective by
consolidating up to 24 remote sites into a single replication target. Replication can also be arranged
to go Site 1 to Site 2 to Site 3 to Site 1 in N-way fashion.
• Minimizes the amount of data to replicate. One of the features of HP D2D replication is that if the
backup software is configured to append to cartridges rather than overwrite them, HP D2D only
transmits manifests to match from the append point, which saves further bandwidth compared to
matching the manifest for the full cartridge each time (i.e., only transmit the manifest for the new
'session' appended to the tape).
• Price point. HP D2D2500/4000/4100 Backup Systems support deduplication as standard and
are better value than products from other leading competitors. Add to that competitive license
costs for replication and the fact that you can replicate up to 16 D2D2500s into a single D2D4000
but only have to purchase a single replication license for the D2D4000. The final result is a very
compelling cost structure for deduplication and replication.

How it Works

HP D2D Backup Systems with HP Dynamic deduplication use a technology called hash-based chunking
to save space. Every unique 4K of data within the D2D deduplication store has its own unique hash
code. After the two D2Ds have been "initialized" with reference data (see
Process) then only new data created at the source site needs to replicate to the target site. This efficiency
in understanding precisely which data needs to replicate can result in bandwidth savings in excess
of 95% compared to having to transmit the full contents of a cartridge from the source site. In addition,
there is some overhead of control data that also needs to pass across the replication link. This is known
as manifest data, a final component of any hash codes that are not present on the remote site and
may also need to be transferred. Typically the "overhead components" are less than 2% of the total
virtual cartridge size to replicate.

D2D Replication Implementation

The following must be performed to implement replication on D2D systems.
Optimizing Rotation Scheme to
HP StorageWorks VLS and D2D Solutions Guide
Implementing the Initialization
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