HP BB118BV - StorageWorks Data Protector Express Package, User Manual, Page: 156 / 365

138 Data Protector Express User's Guide and Technical Reference
In the case of backups done under the D2D2Any option, upon a restore, Data Protector Express may
discover the desired object to be on a virtual library virtual tape cartridge, on media written to the copy
device, or both places. If it is found in both places, restores will normally come from the virtual library as
it is usually the most efficient device to restore from. In the case of a backup that has not yet been written
to a copy device (either the time out has not occurred, the policy was set to
Do Not Copy , or the copy
operation failed), then the restore will come from the virtual library. For cases when the data has been
removed from the virtual library (the
Copy policy is selected, and either Retain data until copied or
Retain data until space is needed options is selected and data has been removed from the virtual
library), the restore will come from the copy device.
The Data Protector Express D2D2Any option not only optimizes space usage in storage folders, it also
optimizes the use of media/storage in the copy device. When data is automatically copied from a virtual
library to the copy device, Data Protector Express remembers the source and destination media (tapes).
The D2D2Any option “remembers” or “associates” these media so that the destination media is retained
(and not erased or overwritten) until the source media is erased or overwritten. To illustrate this concept,
consider a backup to a virtual library that’s subsequently copied to a physical tape cartridge in a physical
loader. When this happens, Data Protector Express will associate the physical tape cartridge with the
virtual library virtual tape cartridge. Regardless of the retention policies on the virtual library virtual tape
cartridge, the associated physical tape cartridge must not be erased or overwritten by any other backup or
media job until Data Protector Express determines that the data can be safely overwritten. The D2D2Any
option determines that it is safe to erase or overwrite the physical tape cartridge when the original backup
has been erased or overwritten under a regular tape rotation schedule.
The “association” described in above is very important for managing and optimizing physical media
usage. For example, without this capability each backup to the virtual library under the D2D2Any option
would eventually lead to consuming another physical tape cartridge, ultimately consuming all available
physical media. Knowing when it is safe to reuse physical media is critical for a cost effective automated
disk-to-disk-to-any solution.
The “association” is accomplished by Data Protector Express when the copy operation is successfully
performed. When this happens, the virtual tape cartridge (media) for the virtual library is converted to a
D2D media folder, and the physical media where the backup was copied is moved into this folder. A D2D
media folder acts as both a piece of media and a media folder. If the D2D media folder is erased or
overwritten, this is the signal to Data Protector Express that the associated physical media can be safely
erased or overwritten. If you want to retain the backups on the associated physical media indefinitely,
then simply move the associated physical media out of the D2D media folder. In this case, the associated
physical media will not be erased or overwritten unless you specifically create a backup or media job to
do that.
Example 1: Virtual backups of a laptop hard disk while an employee travels
An employee who uses a laptop travels frequently on business. While away from the office he uses Data
Protector Express to run daily incremental backups of data files to a local virtual device. These
incremental backups are relatively small, but they provide him with access to backups of his work in the
event that he deletes his work while away from the office and unable to back up his system on the
network. When he returns to the office he connects the computer back to the network, runs a full backup
to physical backup devices and copies the incremental backups from virtual to physical media.
In this example, the backups on virtual media have become obsolete since they are now available on
physical media.