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Tape Offload
Terminology
Direct Tape Offload
This is when a physical tape library device is connected directly to the rear of the D2D Generation 1 products
(D2D2503, 4004, 4009, 2502A, 2504A, 4112A - which are now obsolete) using a SAS host bus adapter.
The D2D device itself manages the transfer of data from the D2D to physical tape AND the transfer is not made
visible to the main backup software. Only transfer of data on VTL devices in the D2D is possible using this
method.
Copies of the data using Direct Tape offload
are unable
to be tracked by the backup application software.
This offload feature is no longer supported on current shipping D2D models.
Backup application Tape Offload/Copy from D2D
This is now the preferred way of moving data from
a D2D to physical tape. The data transfer is managed
entirely by the backup software, multiple streams can be copied simultaneously and both D2D NAS and D2D VTL
emulations can be copied to physical tape. Both the D2D and the physical tape library must be visible to the
backup application media server doing the copy and some additional licensing costs may be incurred by the
presence of the physical tape library. Using this method entire pieces of media (complete virtual tapes or NAS
shares) may be copied OR the user can select to take only certain sessions from the D2D and copy and merge
them onto physical tape. These techniques are known as “media copy” or “object copy” respectively. All copies
of the data are tracked by the backup application software.
When reading data in this manner from the D2D device the data to be copied must be “reconstructed” and then
copied to physical tape and hence the speed is not optimal unless multiple copies can be done in parallel.
Backup application Mirrored Backup from Data Source
This again uses the backup application software to write the same backup to two devices simultaneously and
create two copies of the same data. For example, if the monthly backups must be archived to tape, a special
policy can be set up for these mirror copy backups. The advantage of this method is that the backup to physical
tape will be faster and you do not need to allocate specific time slots for copying from D2D to physical tape.
All copies of the data are tracked by the backup application software.