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Serial ATA A Promising New Alternative for Enterprise Storage Applications O VE RV I E W / E XE C UT I VE S UMMARY For desktop and portable computers, the Parallel Advanced Technology Attachment (ATA) interface is currently the most popular protocol for moving data between the hard drive controller and system memory. Designed to provide a "best of both worlds" solution, Serial ATA (SATA) replaces the existing parallel bus with serial links, and adds features designed to increase the performance, reliability and scalability of ATA-based devices while retaining ATA's significant cost advantage. B AC KGR OUN D As an evolutionary replacement for Parallel ATA, a consortium of industry leaders developed a new storage interface specification called Serial ATA 1.0. This new specification was formally introduced in August of 2001. Serial ATA II, a second iteration of the specification for SATA servers and network attached storage, was published in October 2002. It will allow vendors to further address the needs of networked storage segments via enclosure management, backplane signaling, and cabling and performance improvements. Traditionally, ATA has not supported the requirements of enterprise systems. Traditionally, enterprise storage applications have been dominated by solutions based on the SCSI (Small Computer System Interface) standard, with the more recent entry of Fibre Channel. Systems based on these technologies deliver the high performance and reliability required for mission-critical applications. However, the cost for systems based on SCSI or Fibre Channel can be substantially higher than technologies based on ATA. Storage vendors quickly realized that Serial ATA has distinct advantages over traditional ATA and parallel SCSI that make it a viable alternative for many enterprise storage applications, enabling storage systems at what current pricing models estimate to be one-third the cost of SCSI-based systems. The result is a cost-effective alternative to SCSI technology for all but the most critical direct-attach and networked storage applications. S E R I AL ATA F E A T U RE S AND B E NE F I T S While SATA represents the next generation of ATA interface technology, it departs from ATA with several significant new features and benefits, summarized below. Feature Serial ATA Parallel ATA Parallel SCSI Low-cost implementation Point-to-point connectivity Cyclical Redundancy Checking (CRC) on commands (partial) Hot-plug/hot-swap support Highly