Mass Storage Products - Digital Linear Tape

Table of Contents

DLT Family Overview

In this age of distributed computing, capacity, performance, and reliability are at a premium in tape systems for backing up large LAN's and high-end workstations. Silicon Graphics family of Digital Linear Tape (DLT) devices, comprised of a sled mount tape drive for internal use, a tabletop drive for external use, and the 7 cartridge robotic mini-library, provide a robust solution for these performance oriented environments.

The heart of the Silicon Graphics DLT solution is a 10GB drive that uses some of the highest bit and track densities ever employed in streaming tape drives. The DLT is a single reel approach that allows twice as much tape to be packed inside a cartridge. The net effect of the larger cartridge, single reel design is a device with five times as much recording area on the tape as the 8mm format and 15 times as much as the 4mm format. With equivalent recording densities, the only way that helical formats can match the capacity potential of the DLT streaming cartridge is with the addition of a stacker mechanism to access multiple cartridges.

DLT Performance and Reliability

The DLT format records data in 4K blocks. Each block is split into two 2K blocks which are then written simultaneously to two parallel tracks. This design format doubles the throughput of the device during read and write operations. Splitting the data also increases the reliability of the system. Since DLT uses both Cyclical Redundancy Checking (CRC) and Error Correction Code (ECC), it can internally detect errors and also automatically recover data. In addition, it has a reliability rate of less than one unrecoverable error for 10 to the power of 17 bits read, exceeding both DAT (one error for 10 to the power of 15 bits), and 8mm (one error for 10 to the power of 13 bits).

Additionally, DLT has a calculated undetectable error rate of less than one error in 10 to the power of 30 bits read. If up to 8K of data goes bad within a 32K section, it is still possible to reconstruct the data based on the CRC and ECC information written as part of the DLT format. Furthermore, testing has shown that a single DLT cartridge can be reused over 3500 times before any problems should be experienced. This represents almost ten years of continuous daily use.

P-S-DLT-7

70GB Native, 140GB Compressed High-Performance 0.5-inch Cartridge Tape Mini-Library

The cartridge tape mini library is a SCSI 0.5-inch cartridge tape mini-library with a removable seven cartridge magazine. The library features a formatted capacity of 70GB native, 140GB compressed1 and a sustained user data transfer rate of 1.25MB/second native, 2.5MB/second compressed, providing unattended backup of 140GB in under 16 hours. The mini-library is packaged in a desktop enclosure and is designed and manufactured to Silicon Graphics exacting quality standards.

Feature Summary

Software Support

Software support for the P-S-DLT-7 cartridge tape mini library is provided by Silicon Graphics Networker software or by Epoch Backup (tm) software. The P-S-DLT-7, when combined with Silicon Graphics Networker (tm) software, is a complete workgroup backup and data tape storage solution. When combined with Epoch Backup software, the P-S-DLT-7 becomes an integral part of the Silicon Graphics Hierarchical Storage Management (HSM) strategy.

Designed for Capacity, Performance, and Flexibility

The mini-library design consists of an elevator mechanism that provides direct or sequential cartridge access between the tape drive and cartridge magazine. The magazine loading feature allows the user to manage up to seven cartridges as a complete set. The mini-library subsystem implements the SCSI-2 command set for media management.

At up to 2.5MB/second (9GB/hour), and up to 140GB capacity, the mini-library subsystem has the best capacity and data transfer characteristics of any mini-library mechanism in the industry.

Extensive Operator Interface and Diagnostic Features

The mini-library subsystem provides an operator control panel consisting of labeled LED indicators that display and monitor the sub-system operation. In addition, a "mode select" key provides several options for automatic or manual control. The mode select key also allows access to the drive for servicing by trained personnel.

In the event of drive failure, numerous diagnostic aids are available within the tape drive to quickly isolate problems. These aids include a comprehensive off-line power up self-test, as well as an operator control panel to monitor the subsystem operation.

Ideal for High Duty-Cycle Applications

The digital linear tape recording technology and adaptive control mechanism combined with the mini-library direct-access elevator design make the subsystem a true high duty-cycle product. Critical product reliability specifications include a head life of 10,000 hours and 400,000 mean mechanical cycles before failure.

P-S-DLT/P8-S-DLT

10GB Native, 20GB Compressed High-Performance, 5.25-inch Cartridge Tape Drive

The P-S-DLT and the P8-S-DLT are SCSI 0.5-inch cartridge streaming tape drives. Utilizing data compression and compaction, the drives feature a formatted capacity of 10GB native and 20GB compressed, and a sustained user data transfer rate of up to 2.5 MB/second in an extended 5.25 inch form factor. The P-S-DLT and the P8-S-DLT are designed and manufactured to Silicon Graphics exacting quality standards.

Feature Summary

Designed for Performance

At 1.25MB/second native and 2.5MB/second compressed, the P-S-DLT and the P8-S-DLT offer the best combination of performance and capacity available in the industry. The drive design includes a dual-channel read/write head, DLZ (Digital Lempel-Ziv) high-efficiency data compression, and tape mark directory to maximize data throughput and minimize data access time. The PS-DLT and the P8-S-DLT are also designed with "tape loadable" firmware to provide convenient and flexible micro-code updates.

Leadership Data Integrity

The P-S-DLT and the P8-S-DLT provide powerful, custom Reed Solomon ECC; a custom 64-bit CRC on each 4 kilobytes of data on media; end-to-end 16-bit CRC on each record overlapped with parity from the SCSI bus; and internal parity checking on the cache buffer. These features produce an unequalled hard error rate specification of one error in 10 to the power of 17 bits--the best data integrity specification of any tape technology available in the industry.

Extensive Diagnostic Features

In the event of a failure, there are numerous diagnostic aids available within the tape drive to isolate problems quickly. These aids include a comprehensive off-line self-test and a scratch-pad memory to store and retrieve cumulative error information.

Ideal for High Duty-Cycle Applications

The digital linear tape recording technology, accurate tape guiding system, and adaptive control mechanism make the P-S-DLT and the P8-S-DLT true heavy-duty tape drives. Critical reliability specifications include a head life of 10,000 hours, 500,000 tape media passes and an MTBF of 80,000 hours.

P-S-DLT-7 Mini-Library Specifications

Tape Drive 

------------------------------------------------------------------------
Capacity (formatted               10GB native, 20GB compressed*           
Read/write speed                  120 in/s, streaming                     
Search speed                      120 ips                                 
Sustained transfer rate           1.25MB/second native, 2.5MB/second com  
                                  pressed                                 
Peak transfer rate (SCSI bus)     5MB/s synchronous                       
Repositioning time                1.3s                                    
Hard error rate                   1 x 10 to the power of 17 bits read                         
Undetected error rate             1 x 10 to the power of 30 bits read (calculated)         
                                                                          
------------------------------------------------------------------------
* indicates 140GB Capacity and 2.5MB/sec performance assumes 2:1 data compression.

Recording Medium 

-------------------------------------------------------
Tape       0.5 inch metal particle (MP), 1,500 Oe, 0.5   
           mil thick                                     
Length     1,100 ft                                      
Cartridge  CompacTape (tm) III, 4.1 in x 4.1 in x l in   
-------------------------------------------------------

Mini Library

P-S-DLT/P8-S-DLT Specifications

Performance 

---------------------------------------------------------------------
Read/write speed               120ips, streaming                       
Search speed                   120 ips                                 
Sustained transfer rate        1.25MB/second native, 2.5MB/second com  
                               pressed                                 
Peak transfer rate (SCSI bus)  SMB/s synchronous                       
Repositioning time             1.3s                                    
Hard error rate                1 x 10 to the power of 17 bits read                         
Undetected error rate          1 x 10 to the power of 30 bits read (calculated)         
                                                                       
---------------------------------------------------------------------

Data Organization 

-----------------------------------------------------------------------
Recording format (physical)   128 track serial serpentine, fixed block   
Recording density             62,500 bits/in                              
Data Encoding                 2,7 RLL                                    
Track density                 256 tracks/in                              
Read-write head               Two-channel, ferrite w/MlG                  
Data Compression Algorithm    DLZ Maximum capacity formatted) 20GB        
                                                                         
-----------------------------------------------------------------------

Recording Medium 

--------------------------------------------------------
Tape         0.5 inch metal particle (MP), 1,500 Oe, 
             0.5 mil thick                                      
Length       1,100ft                                        
Cartridge    4.1 in x 4.1 in x 1 in                         
                                                          
--------------------------------------------------------

Interface 

-------------------------------------------------------------
SCSI-2 embedded controller, single-ended 8bit SMB/sec transfer 
rate for external device and for sled-mount device
-------------------------------------------------------------

Operating Environment 

---------------------------------------------
Temperature range    10C to 40C                
Relative humidity   20% to 80% noncondensing   
Altitude (maximum)  8,000 ft                   
Noise level          35 dB                     
                                               
---------------------------------------------

Nonoperating Environment 

---------------------------------------------------------------
Temperature range                -40C to 66C (excluding media)   
Relative humidity               10% to 95% noncondensing         
Altitude (maximum)              30,000 ft                        
---------------------------------------------------------------

Power Requirements

for P8-S-DLT (internal, sled-mount device)
for P-S-DLT (external device)




Physical Characteristics


P-S-DLT (external device) 


    
---------------------------------
Height      3.75 in
Width       6.0 in 
Length     12.25 in
Weight      6.5 lb
---------------------------------




P8-S-DLT (internal, sled-mount device)


    
--------------------------------------------
Height   3.235 in 
Width    5.7 in 
Length   9 in (from bezel to pins) 
Weight   5 lb
--------------------------------------------





Reliability


----------------------------
Drive MTBF     80,000 hrs
Head life      10,000 hrs
Media         500,000 pass
------------------------------