Parallel interfaces transmit multiple bits concurrently, each on it’s own separate data path requiring precise timing to maintain proper bit synchronization. As transfer rates increase this timing becomes more difficult.
In contrast serial interfaces transfer all bits one after another on a single data path with no timing issues to slow throughput. Parallel devices daisy chain devices together on a single bus reducing performance as each device waits it’s turn to access the bus.
Serial interfaces employ point-to-point architecture providing each device with a dedicated signal path to maintain devices regardless of how many devices are connected. The shared bus architecture of the parallel bus interfaces severely limits the number of devices that can be attached to the bus. In contrast, the point-to-point architecture of serial interfaces allows for enormous scalability without the devices configuration limitation of parallel interfaces.
Parallel ATA was the primary internal storage interconnect for the desktop, connecting the host system to peripherals such as hard drives, optical drives, and removable magnetic media devices. Parallel ATA is an extension of the original parallel ATA interface introduced in the mid 1980s.
Serial ATA or SATA is the next generation internal storage interconnect, designed to replace parallel ATA technology. Serial ATA is the proactive evolution of the ATA interface from a parallel bus to serial bus architecture. This architecture overcomes the electrical constraints that are increasing the difficulty of continued speed enhancements for the classic parallel ATA bus.
Serial Attached SCSI or SAS is an evolutionary development that combines the best of both serial technology and SCSI technology. SAS seamlessly integrates these two technologies into a new standard that meets the ever-growing needs of evolving enterprise. SAS overcomes many of parallel SCSI’s drawbacks, yet maintains the reliability of its parallel predecessor by integrating its robust SCSI command set.
SATA and SAS technologies were made possible by the efforts of leading storage vendors who teamed together to create optimal industry standards from which all industry partners will benefit. The standard specifications were adopted by their respective trade association and approved by the American National Standards Institute (ANSI). SAS builds on 20 plus years of reliable SCSI technology. Its enhancements, reliability and universal compatibility will easily meet the need of enterprise for the years to come. Serial attached SCSI products will enable system builders to offer systems that significantly reduce data center infrastructure costs.
SAS provides the path through which the deployment of SATA drives in the enterprise offers the greatest strategic benefit, namely the freedom to build and select the most appropriate RAID sets within a single chassis for a given task.
Serial attached point-to-point full duplex SAS and SATA architecture and compact connectors are ideal matches for enterprise disk drives that enable transitioning to more cost effective space efficient storage array appliances.