End To End Recovery - Data Center To Data Center - HP D2D Manual

3. Configure Media Agent and shared disk devices for both D2D libraries on Commserve.
4. Configure a replica disk library (CommVault terminology) for both D2D-A and D2D-B associated
with the same Media Agent on Commserve.
If we have a disaster on Site A but Commserve remains operational, it is possible to recover the
data from Site B by selecting the Media Agent path for the replica disk library and restoring over
the secondary path link (GbE).
As Commserve at Site A did not physically write the data to D2D-B (it was written by the low
bandwidth replication process), and there are no entries in the CommCell database for D2D-B,
you might think that recovery is not possible. However, since D2D-A and D2D-B share the same
Media Agent, a full recovery from Site B is possible because, with CommVault, meta data about
the contents of a backup is held in an index that is appended to each backup set.
When completing a restore from D2D-B, the first time a recovery is undertaken, the index information
for the backup set has to be retrieved from the backup in order to select which files to recover.
This index is recovered to the local index cache on the Media Agent (in this case the Commserve),
and is therefore available immediately for subsequent restores.
The index cache directory is the directory in which index data resides. Each Media Agent maintains
an index cache for the data protection operations performed using that Media Agent. The index
data maintained in the index cache is accessed by the system during data protection, browse,
and data recovery operations.
The index cache is maintained on a least recently used (LRU) basis. As the capacity of the cache
is reached, those index data files that have been least recently accessed are overwritten with the
new index data. If a data protection, browse and data recovery operation requires index data
that is either no longer in the cache or not accessible to the operation, the index data is recovered
from the media.
To ensure that other files do not use up disk space that is needed for index data, you can create
a partition specifically for the index cache directory. The partition must be large enough to
accommodate four percent of the estimated amount of data managed by the Media Agent.
During the Media Agent installation, the install program prompts for an index cache location for
the specific Media Agent. This information can be viewed or modified from the Catalog tab of the
Media Agent Properties dialog box.
End to end recovery – data center to data center
In this scenario there are data centers in two locations. Site A is the production location, where
live backups of the production data takes place; and Site B is a Disaster Recovery location.
Two D2D Backup Systems are provided, one in each location, together with dedicated Media
Agent servers for each library. At Site A, the Commserve acts as the Media Agent for the local
D2D Backup System (D2D-A), whilst the second Media Agent server is connected to D2D–B at the
Disaster Recovery location (Site B).
Both D2D Backup Systems and Media Agents are configured as a CommVault replica disk library,
with the primary path (read/write) through Media Agent connected to D2D-A; and a read-only
path via Media Agent connected to D2D-B.
42 End to End Disaster Recovery Process