Overview
ISO/IEC 14776-413:2007 - "Information technology - Small Computer System Interface (SCSI) - Part 413: SCSI Architecture Model‑3 (SAM‑3)" defines a reference architecture for the SCSI protocol family. The standard describes the abstract structure and expected behaviour common to all SCSI I/O system implementations for peer‑to‑peer host/peripheral communications (bus widths of 8 or 16 are supported). SAM‑3 provides the model used by SCSI device vendors, operating system developers, and storage architects to design interoperable SCSI software and firmware components.
Key Topics
- SCSI architecture model: distributed service model, client–server model, structural and domain models, and the service delivery subsystem.
- SCSI devices and ports: definitions for initiator, target, and target/initiator devices; multi‑port devices; port identifiers and port naming conventions.
- Logical units and LUN addressing: logical unit concepts, minimum LUN addressing, single‑level and extended LUN structures, well‑known LUNs and addressing methods.
- Command model: Execute Command procedure, Command Descriptor Block (CDB) handling, status codes and precedence, and command lifetimes.
- Data transfer services: transport protocol services for Execute Command, Data‑In/Data‑Out delivery, and terminate data transfer mechanisms.
- Task and task management: task tags, lifetimes, abort mechanisms, task management functions (ABORT TASK, ABORT TASK SET, CLEAR ACA, LOGICAL UNIT RESET, etc.).
- Exception handling: CHECK CONDITION handling, Auto Contingent Allegiance (ACA), overlapped commands, sense data, Unit Attention conditions.
- Events and notifications: SCSI events overview, event‑triggered Unit Attention conditions, and event notification transport services.
- Nexus model: relationships among initiator/target ports and logical units (I_T nexus), and models for dependent logical units.
Applications
- Implementing SCSI stacks in firmware, device drivers, and storage controllers.
- Designing SCSI target devices (disk arrays, tape libraries, SAN endpoints) and multi‑port device behavior.
- Defining LUN addressing and interoperability rules for storage provisioning and virtualization.
- Developing OS kernel I/O subsystems and transport layers that conform to SCSI task and event semantics.
- Creating test suites and compliance tools for SCSI implementations.
Who uses it
- Storage hardware vendors and firmware engineers
- Operating system and driver developers
- Storage system architects and integrators
- Test labs and standards compliance teams
Related standards
- Part of the ISO/IEC 14776 SCSI standards series; SAM‑3 complements other SCSI transport and command set documents used to define complete SCSI implementations.
Keywords: ISO/IEC 14776-413:2007, SCSI, SAM-3, SCSI Architecture Model, Small Computer System Interface, LUN addressing, task management, CDB, Auto Contingent Allegiance.
Open preview (PDF)Information technology — Small Computer System Interface (SCSI) — Part 413: SCSI Architecture Model -3 (SAM-3)
