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Author: Paul Vogt, Sr. Director, Product Management
Xyratex International, Ltd.

The Need for Serial Attached SCSI (SAS)
In order to understand the justification for the industry's investment in a new I/O technology standard, it is useful to look at a typical parallel Ultra320 SCSI bus configurations. This type of configuration was a common Direct Attached Storage (DAS) implementation in an enterprise server configuration in the early 2000's. Illustrated are two boot drives in the system as well as an additional Ultra320 SCSI JBOD (Just a Bunch of Disks) connected to the SCSI adapter in order to increase the capacity of the system.

Author: Susan Bobholz, Market Development Manager
Intel

Serial Attached SCSI (SAS) is the logical evolution of the traditional parallel SCSI interface, and it represents the continuation of more than 25 years of technology development and infrastructure investment. In SAS, the SCSI protocol is transported over a serial interface. Compared to the existing parallel SCSI interface, SAS enables faster device interconnect speeds, simpler cabling and improved system reliability, while preserving existing SCSI capabilities. SAS also improves connectivity to larger numbers of drives and also enables compatibility with Serial ATA (SATA) drives. The SAS interface standard was developed by the T10 Technical Committee of the International Committee for Information Technology Standards (INCITS). The latest specification "Serial Attached SCSI version 1.1" has been adopted by the American National Standards Institute (ANSI). A wide variety of SAS products has been shipping for several years including hard drives, controllers, servers and networked storage systems.

What is SAS?
SAS is the high-speed serial successor to Ultra320 SCSI as well as an I/O infrastructure that provides for a wide range of storage solutions. SAS goes beyond a mere disk drive interface; it provides a set of components that include connectors, cables, and expanders that can be used to deploy a large number of solutions into the storage and server market. While SAS preserves the traditional SCSI usage model, it widens the types of applications and markets it can serve including blade storage, tiered storage and near-line storage, and shared storage between hosts.

Author: Cameron T. Brett, Manager, Product Marketing
PMC-Sierra, Inc.

Putting Serial Attached SCSI (SAS) to work is relatively easy. Server and storage solutions can be created ranging from simple direct-attached storage (DAS) in servers to high-availability, switched rack environments. To look at these solutions, it is best to understand the SAS building blocks first.

Author: Kent Bransford, Senior Technical Editor,
Seagate Technology

The following is an actual case study, illustrating how SAS technology is a key enabler of high-performance business intelligence storage solutions that utilize the concept of a "server brick."

Microsoft Project REAL
The server brick concept was developed by Microsoft while working on Project REAL (Reference implementation, End-to-end, At scale, and Lots of users). The project involved a major US retailer with over 800 stores in the US and more than 40,000 employees. While the retailer's sales and data warehouse was initially 1.5TB in size, by the project's completion it had grown to over 4TB and was expected to continue this rapid expansion in the future.