SCSI COMMUNICATION INTERFACE

Table 6-1SCSI bus phases and information transfer phases

 

 

Bus Phase

Description

 

 

Transfer:

The Message phases help manage the physical path between the initiators and targets.

ƒMessage In/ ƒ In the Message In phase, the tape drive sends a message to the initiator. In the Message

Message Out

Out phase, the initiator sends a message to the tape drive.

ƒCommand ƒ In the Command Out phase, the initiator sends a command to the tape drive.

Out

Commands contain information about what actions the tape drive should perform.

ƒData In/ ƒ In the Data In phase, the tape drive transfers data to the initiator. In the Data Out

Data Out

phase, the initiator transfers data to the tape drive.

ƒStatus In ƒ In the Status In phase, the tape drive returns a status byte to the initiator. The status byte indicates the results of the command’s execution.

SCSI MESSAGE SYSTEM

The SCSI message system allows communication between a SCSI initiator and the VXA-320 tape drive for interface management. This message system or command set is separate from the SCSI command protocol used to control the operation of the tape drive. A message can be one byte or multiple bytes. Table 6-2describes the SCSI messages that the tape drive supports.

Table 6-2SCSI messages supported by the tape drive

Message

Hex

Description

Code

 

 

 

 

 

Task

00h

The tape drive informs the initiator that the execution of the command was

Complete

 

completed and that it sent a valid status byte to the initiator.

 

 

 

Extended

01h

Synchronous Data Transfer Request (01h) The tape drive supports

Messages

 

synchronous data transfer.

 

 

 

 

 

Wide Data Transfer Request (03h) The tape drive supports wide data transfer.

 

 

 

 

 

Parallel Protocol Request (04h) The tape drive supports negotiating a

 

 

synchronous data transfer agreement, a wide data transfer agreement, and setting

 

 

the protocol options between two SCSI devices.

 

 

 

Save Data

02h

The tape drive requests that the initiator copy the current data pointer for possible

Pointer

 

use by the Restore Pointers message during error recovery.

 

 

 

Restore

03h

The tape drive informs the initiator that it did not properly receive a block of data

Pointers

 

or the command descriptor block (CDB) and that the data needs to be transferred

 

 

again.

 

 

 

Disconnect

04h

The tape drive informs the initiator that it plans to disconnect from the SCSI bus

 

 

and that a reconnect will be required later.

 

 

 

Initiator

05h

The initiator informs the tape drive that an error occurred. The tape drive can retry

Detected

 

the operation.

Error

 

 

 

 

 

OCTOBER 2006

VXA-320 TAPE DRIVE

 

 

 

 

 

 

 

 

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Tandberg Data VXA-320 (VXA-3) manual Scsi Message System, Message Hex Description

VXA-320 (VXA-3) specifications

Tandberg Data VXA-320 (VXA-3) is a sophisticated backup solution designed for businesses seeking reliable data storage and backup capabilities. It is part of the renowned VXA series, heralded for its innovative approach to data archiving and its robust performance in diverse operating environments.

One of the standout features of the VXA-320 is its impressive data transfer rate, which reaches up to 36 GB per hour. This capability significantly enhances backup speed, making it a suitable choice for organizations with extensive data storage needs. The device supports a native capacity of 160 GB per cartridge, which can be expanded to 320 GB when data is compressed. This dual-layer cartridge system ensures that users can efficiently manage large volumes of data without constantly needing to interchange tapes.

The VXA-320 employs the unique VXA tape format, characterized by its advanced error correction and data integrity features. This format minimizes data loss risks and ensures reliable restoration of information. Additionally, the VXA-3 incorporates a one-inch data path, allowing it to handle higher track counts and thereby achieve better storage density. This design improves the efficiency of data retrieval and archiving processes.

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The device also includes an intelligent tape management system that tracks the status of backup jobs and the usage of tapes. This feature facilitates easier management of the backup process and ensures users remain informed about the condition of their storage media.

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