DEC-TA79+TA81-MagneticTapeSubsystems

This document describes Digital's TA79 and TA81 magnetic tape subsystems, designed to enhance VAXcluster systems by providing shared, high-performance, and reliable data storage.

Key Benefits and Features:

1. Shared Resources for VAXclusters: Both subsystems function as shared resources across a VAXcluster, improving data availability, reducing user contention for drives, and offering cost savings compared to non-clustered systems.
2. HSC Storage Server Integration: They connect to HSC50 or HSC70 Storage Servers, which offload I/O overhead from the main CPUs (via Digital Storage Architecture - DSA), increasing overall system throughput.
3. Enhanced Backup Performance: The HSC Storage Servers' "Local Backup Utility" allows for very high-speed disk backups and restores that run offline, without involving the host CPUs, significantly reducing backup times.
4. High Data Integrity: Both models feature outstanding data integrity through read-after-write verification, vertical parity checks, and error correction (ECC/CRC in GCR mode) without CPU intervention.
5. Dual-Density Recording: They support both Phase Encoded (PE) and Group Code Recording (GCR) formats (1600 bpi and 6250 bpi respectively), allowing compatibility with industry-standard tapes.

Key Differentiations Between TA79 and TA81:

• TA79 (High-Performance):

  • Top-of-the-line, with a sophisticated start/stop design ideal for journaling, transaction processing, and high-speed backup.
  • Offers significantly enhanced reliability due to re-engineered electronics and mechanical components.
  • Features automatic tape loading and fast-access windows.
  • Can act as a master unit, supporting up to three TU79 (and older TU78) slave tape transports.

• TA81 (Midrange/Economical):

  • More economical and mechanically simpler, primarily a streaming tape drive.
  • Best suited for sustained I/O applications like high-capacity disk backup and data archiving.
  • Features a shorter, manual tape path for fast loading.
  • Does not support slave transports.

Both subsystems are designed for ease of use and maintenance, include built-in diagnostics, and offer upgrade kits for existing TU series drives to protect customer investment.