User`s guide

Shows the device configuration after the clone is complete.
Shows the mirrorsets after the clone is complete.
Shows the storagesets after the clone is complete.
7.3.13 Command Disks (HSJ and HSD30 Array Controllers)
A special storage configuration is available for communication with generic SCSI
devices. The concept centers around a virtual unit, called a command disk, that
allows an MSCP-based host to control any physical SCSI device.
This feature uses the MSCP read and write operations as a transport for SCSI
commands. In other words, the command disk will appear to the host as simply
another disk behind the controller. However, the command disk resides entirely
in approximately 10 KB of controller memory. The command disk exchanges SCSI
commands, SCSI status, and data with the SCSI device. The setup is necessary
in order for MSCP to transfer the SCSI information required when performing
anything more than simple device reading or writing.
7.3.13.1 Uses for Command Disks
Although a command disk will allow you to perform a number of operations,
including downloading of microcode into a SCSI device’s processor memory, the
example presented in this manual is that of a tape library.
A tape library contains standard tape devices plus a robotic mechanism for
selecting and loading cartridges from a pool of tapes. (Such mechanisms are also
known as ‘‘jukebox’’ style loaders, or medium changers.) The loader is a good
application for a command disk because SCSI commands are needed to control
the robotic movement within the device.
7.3.13.2 Creating a Command Disk
You must configure a command disk at the controller and the host level.
Note
If you have an HS array controller configuration without a cache
module option, Digital recommends that you create no more than six
command disks, to avoid degrading the performance of DILX with the
Auto-Configure option.
7.3.13.3 Controller Setup
The following explains what you must do at the controller level to create a
command disk for a loader. Note that you can only assign one SCSI device to
each command disk.
Note
Starting with HSOF Version 2.5, multiple LUNs are supported under
HSJ and HSD30 array controllers with selected tape loaders. Tape drives
will use LUN 0 and the tape loaders use LUN 1.
1. Add the tape device serviced by the loader robot.
2. Add the tape device as a unit visible to the host.
3. Add the loader mechanism using its PTL location.
Diagnostics and Utilities 7–101