ANSI INCITS 491

Abstract

The set of SCSI standards specifies the interfaces, functions, and operations necessary to ensure interoperability between conforming SCSI implementations. This standard is a functional description. Conforming implementations may employ any design technique that does not violate interoperability. This standard defines the protocol requirements of the SCSI / ATA Translation Layer (SATL) to allow conforming SCSI / ATA translating components to interoperate with ATA devices, SCSI transports, and SCSI application layers. The SATL covers a range of implementations that use ATA devices to emulate the behavior of SCSI devices as viewed by the SCSI application layer. The primary focus of this standard is to define SCSI / ATA Translation for an ATA device (see 3.1.7).  Where possible, this standard defines SCSI / ATA Translation in a manner that is consistent with the SAM-5, SPC-5, SBC-4, and ZBC standards. In some instances, the defined function of an ATA device is different from corresponding functions defined for SCSI target devices (e.g., many ATA devices provide no means to abort a single ATA queued command). The translation defined in this standard, in such cases, may not be consistent with other SCSI standards. However, in such cases, this standard specifies the expected behavior, and in what manner it is inconsistent with the behavior specified in other SCSI standards. The objective of this standard is to allow an interoperable set of SCSI functions while minimizing the complexity of the SATL and preserving compatibility with existing SCSI application clients. The objectives of the SATL are: a) to provide host computers with device independence with respect to the ATA devices and with respect to various implementations of the translation layer used to emulate the behavior of SCSI target devices; b) to define common features and functions representing a subset of the capabilities available in SCSI devices that apply to SCSI / ATA Translation implementations; c) to define common methods to manage aspects of ATA devices that do not map to previously defined features and functions of SCSI, with provision made for the addition of special features and functions; and d) to provide consistent means for discovery and control of optional SCSI features that may or may not be emulated in SCSI / ATA translator implementations. These means are provided by specifying how transport specific features and functions are represented in a mixed-domain topology in a manner consistent with management of devices in a SCSI domain.