Understanding Automigration Concepts; Echo Copy Concepts - HP StorageWorks 6000 - Virtual Library System User Manual

Understanding Automigration Concepts

Before using automigration, review the information in this section. This will allow you to create copy
pools and automigration policies appropriate to meet your storage needs.

Echo Copy Concepts

Echo copy acts as a transparent disk cache to the physical library, so that the backup application
writes to virtual cartridges in the virtual library. Automigration then automatically schedules the copies
from virtual cartridges to physical cartridges with matching barcodes, based on the automigration
policies the user establishes.
Echo copy is managed through the automigration software, not the backup application. For that
reason:
• The destination library is not visible to the backup application, so it does not need licensing.
• Copy traffic is no longer routed through the SAN.
• All destination tapes created by echo copy are in the native tape format, so they can be restored
directly from any tape drive or library that is visible to the backup application.
When determining whether to use echo copy pools, remember:
• The backup application will not be aware of any copy failures.
• Any mistakes in destination library media management will also affect the virtual cartridges. For
example, if new tapes are not loaded into the destination library, the physical copy will not exist.
• The destination library can only be used for copy operations.
• Echo copy is a full tape copy, rather than an incremental change copy, so it can be an inefficient
use of media if you are using non-appending copy pools in your backup jobs.
An echo copy pool is used to define which destination library slots are to be echoed into a specified
virtual library. Automigration then monitors the echo copy pool slots to detect cartridge loads/ejects
in the destination library, and automatically synchronizes the virtual cartridges to the destination
cartridges, creating the matching virtual cartridges as needed.
This means that when new destination tapes are loaded, automigration will automatically scan them
(read the backup application headers) and then automatically create matching virtual cartridges in
the virtual library specified for that echo copy pool.
NOTE:
The automatic scanning of new cartridges can take a long time if all the tape drives in the destination
library are busy with higher priority operations such as copies. Therefore, it is best to load new tapes
when copies are not running.
Data written to echoed virtual cartridges will be automatically copied onto matching destination tapes
based on the echo copy policy. An echo copy policy defines for each source virtual library the copy
window (start and end times), the copy on eject option, and the time in days for expiration after eject.
If destination tapes are ejected, the matching virtual tapes are automatically moved to the firesafe
and are deleted at the policy-defined expiration time. This ensures the device does not fill up its disk
space with older cartridges. See
virtual tapes are ejected by a backup application, the matching destination tapes are also automatically
ejected into the destination library mailslot when the copy operation is complete. When an echo copy
is ejected (mailslot eject box is checked), the echo copy is performed, then the eject is carried out.
This results in the echo copy being placed in the device's firesafe and maintained according to the
72 Automigration/Replication
"Creating an Echo Copy Pool" on page 80 to create a policy. If