HP LTO 4 FC Providing pass-through mode, Requirements for drivers and logical device managers

1.Clean the heads and try the operation again.

2.If the ‘Clean’ LED is lit again, repeat the operation with another tape cartridge. If this clears the ‘Clean’ LED, it indicates that the original cartridge is at fault. Copy the data from the cartridge onto a new one and discard the old cartridge.

The ‘Clean’ LED is cleared by a cleaning cycle.

Providing pass-through mode

It is important for Drivers and Logical Device Managers to provide a pass-throughmode that can return information or commands specific to a vendor’s product. The need for this is two-fold:

•Systems must support a great variety of new devices.

•All tape drives are similar to a degree; Drivers and Logical Device Managers tend to provide connectivity based on the assumption that 80% of all SCSI tape drives behave identically.

Pass-through mode offers the following advantages:

•Peripheral manufacturer can provide value-added diagnostics and support applications over and above those that may be shipped with a system or application.

•System supervisors and operators can take advantage of specific product features otherwise excluded because the driver or manager only caters for 80% of SCSI drives.

•Technical support people have access to low-level device-specific information likely to be unavailable otherwise.

Requirements for drivers and logical device managers

Drivers and Logical Device Managers must allow the user to do the following:

1.Create either a 6-byte, 10-byte, 12-byte or 16-byte SCSI Command Descriptor Block.

2.Allocate a write buffer or file for any data associated with the SCSI command that will be sent to the drive.

or

Allocate a read buffer or file for any data associated with the SCSI command that will be returned by the drive.

3.Link the command and data buffers.

4.Launch the command.

5.The driver should use its standard CHECK CONDITION and REQUEST SENSE routines to report whether the command completed successfully or not. The caller must have access to the raw

REQUEST SENSE data.

6.View any returned data.

90 Exception handling

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