Serial ATA technology, 4th edition

Introduction

Serial ATA (SATA) has evolved beyond a serial replacement for parallel ATA in desktop computers. SATA is now an

alternate, lower cost solution for non mission-critical enterprise storage applications. SATA technology can provide

adequate scalability and hot plug capability needed for server and network storage devices at the entry to mid-

range levels.

The Serial ATA Revision 3.0 and 3.1 specifications increase the maximum data transfer rate from 3 gigabits per

second (Gb/s) to 6 Gb/s and add new features. The higher speed provides more headroom for solid-state drives

(SSDs) and for using multiple disk drives through expanders. New features such as native command queuing (NCQ)

and NCQ management improve performance. NCQ lets a drive rearrange the order of requests from the host to

maximize throughput, and NCQ management lets the host manage and process outstanding NCQ commands.

This technology brief describes key technologies in the SATA specification, its implications for SATA storage

devices, the interoperability of SATA and Serial Attached SCSI (SAS) devices, and examples of internal and

external SATA topologies. Table 1 in the Appendix contains terms related to SATA technology.

SATA devices and interoperability with SAS devices

SATA devices include initiators (controllers or hosts) and targets (hard drives, optical disk drives, and solid-state

drives). The initiator attaches to one or more targets or expanders. You can increase the number of SATA targets

attached to an enclosure by adding a SATA-compatible SAS expander (low-cost high-speed switch). The SATA

Tunneling Protocol (STP) enables SAS controllers to communicate with SATA devices, allowing you to deploy both

SAS and SATA drives.

Figure 1: This is an example of SATA/SAS connectivity.

Initiators

An HP initiator is an embedded SATA or SAS controller or a PCIe SAS controller. Our embedded controllers only

support internal devices. We have Host Bus Adapter (HBA) and Smart Array options that support internal devices,

external devices, or both. We support SATA optical drives only on an embedded SATA controller.