Overview
ISO/IEC 14776-322:2007 - Information technology: Small Computer System Interface (SCSI) - Part 322: Block commands-2 (SBC-2) defines command set extensions that enable efficient peer-to-peer I/O operation of SCSI direct-access block devices (disks, flash media, removable media, array controllers). Published as the first edition in 2007 by ISO/IEC, SBC-2 extends and specifies block-level commands, device models, protection information, error reporting and power/state behaviors for modern SCSI block devices.
Key Topics
- Direct-access block device model - logical blocks, media types (rotating and memory media), removable media, initialization and ready states.
- Block command set - standardized commands and variants for block I/O including numerous READ and WRITE forms, READ CAPACITY, READ DEFECT DATA, FORMAT UNIT, REASSIGN BLOCKS, VERIFY, START STOP UNIT, SYNCHRONIZE CACHE, PRE-FETCH, and others.
- Protection information model - logical block guard data, CRC generation and checking, and mapping of protection information to commands.
- Error reporting and sense data - standardized descriptors and handling to support reliable diagnostics.
- XOR and array operations - models for XOR-based operations used by storage arrays (update, regenerate, rebuild) and stripe consistency considerations.
- Caching, write failures and medium defects - cache semantics, error handling for write failures, and defect management.
- Power and state management - START STOP UNIT state machine, power/standby/idle transitions and their effect on command behavior.
- Reservations and grouping - multi-initiator reservation behavior and grouped command handling.
Applications
SBC-2 is essential for anyone building, integrating or validating SCSI block storage solutions:
- Storage device manufacturers - firmware and controller developers implement SBC-2 to ensure interoperable block commands and protection information.
- Storage array and RAID controller vendors - use XOR models and rebuild/regenerate command semantics for parity and array operations.
- Operating system and hypervisor developers - implement SCSI drivers and storage stacks that rely on standardized READ/WRITE, caching and power semantics.
- System integrators and test labs - validate device compliance, error reporting and performance under different media types.
- Enterprise IT architects - reference SBC-2 when specifying procurement, interoperability and data protection requirements.
Related Standards
- SCSI Primary Commands (SPC series) - overarching SCSI command framework.
- Other parts of the ISO/IEC 14776 (SBC) family - related block command specifications and updates.
Keywords: ISO/IEC 14776-322:2007, SBC-2, SCSI block commands, direct-access block devices, READ CAPACITY, protection information, XOR, START STOP UNIT, SCSI standard.
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