BackBox H4.00 User Manual

Product Description
15 BackBox H4.00 User Manual
• Not configured as a device reserved for explicit allocation (with an
explicit only attribute), and
• Not configured as a device reserved for a volume class that is not the
class of the volume to mount.
Once those mandatory criteria are met, the devices are dynamically assigned to
distribute the workload across available SCSI/FC ports and VTCs. The preference
criteria are listed below, beginning by the most important one:
1. Rank of the Data Store route. All drives of a route (i.e. a VTC) with a lower rank
are used before using the drives of the next route.
2. For a restore, use the same VTC as at backup time
3. Use the same VTC for continuation volumes of a multi-volume backup or restore
4. Use the drives reserved for the volume class of the volume to load
(drives without reservation are acceptable as second choice)
5. Load balancing by physical port: use the host’s SCSI/FC port that is currently
being used for the smallest number of tape emulations
6. Load balancing by VTC: use the VTC that is currently processing the smallest
number of virtual volumes
7. Load balancing by VTC: use the VTC that is currently processing the smallest
number of virtual volumes
8. For S-Series, prefer BRIDGE to direct SCSI connection to the VTC
9. Finally, use the drives in a round-robin fashion, choosing the one that has been
unused for the longest time
Tape drive emulation
To the NonStop host, a BackBox virtual tape drive appears as a physical drive
connected by SCSI or Fibre Channel.
The drive appears as LTO3 (i.e. using LTO3 or LTO2 media type) by default, unless
otherwise specified in the VT internal configuration files.
3480 media type can also be supported for Guardian nodes where the tape system is
not recent (G06.31 or SPR T0021G05^ABW, H06.13 or SPR T0021H01^ABZ).
LTO4 is also supported, mainly for supporting HP VLE encryption with ESKM.
BackBox supports all NonStop tape I/O commands that affect the content of data on
tape and the current position on the media. How data is actually stored is controlled
by the BackBox configuration and the Data Store software/hardware, and is
transparent to Guardian.
Automatic unload
In normal processing, volumes are unloaded by a SCSI or FC command sent by the
NonStop tape system when a tape application ends. This unload event is forwarded