STA

Authors: Paul Vogt, Senior Director of Product Management
               Dale Lafferty, Director of Alliances and Partnerships
               Xyratex International

Introduction
There is a technology shift taking place in enterprise storage environments that could help IT departments address some of the constraints the economy is placing on their budgets. The venerable Fibre Channel (FC) drives have been a staple in the enterprise for over a decade and their replacement by SAS drives is now in full force. Virtually all large storage system market leaders now offer enclosures with Serial Attached SCSI (SAS) disk drives in lieu of FC. While this may be good news for departmental budgets, how will the IT decision-maker feel comfortable with the long term reliability of SAS drives? There is good news about enterprise drive technology; SAS drives are enterprise proven. Market analyst firm, IDC, projects that SAS and SATA drives will replace FC drives in enterprise storage over the next five years.¹

(1) IDC: Worldwide Hard Disk Drive 2009-2013 Forecast and Analysis: A Post Crisis Fundamental Shift, May 2009, Doc # 218262

Author: Chaz Nichols, Global Channel Marketing and Kent Bransford, Sr. Technical Editor,
Seagate Technology

"Use the right tool for the job" is a time-honored maxim that's particularly relevant to developers and system builders seeking to deliver maximum value to their customers. Data center storage requirements continue to expand and diversify, challenging IT professionals to move beyond the traditional "speed or capacity" dichotomy to also address such issues as power consumption, system cooling, data center footprint, ease of data migration and more.

Efficiently meeting such a broad spectrum of storage requirements with only a narrow range of hard disk drives (HDDs) from which to choose is simply not possible...a fact to which many storage professionals can ruefully attest. In response to this dilemma, Seagate has recently made four compelling additions to its comprehensive Savvio, Cheetah and Barracuda ES enterprise disk drive families.

Storage solutions play a fundamental role in shaping data center footprint, power and cooling profiles, and Seagate has purpose-built its new Savvio 15K, Cheetah 15K.6, Cheetah NAS and Barracuda ES.2 Serial Attached SCSI (SAS) disk drives to maximize data center ROI. By combining superior performance and capacity with significantly reduced space and energy requirements, Seagate HDDs enable you to build higher performing, greener and more eco-friendly systems.

Author: Steve Denegri
Independent Data Storage Analyst

The Industry in Aggregate

It may have taken longer than expected, but RAID arrays equipped with SAS are now shipping. IBM is the first to get in the game with the launch of its EXP3000 array at the end of August. Soon to come are SAS-based RAID boxes from the likes of Dell, EMC, Hitachi, HP, and Sun. NetApp enters the fray, too, with filers based on SAS by year-end.

Almost universally, the new SAS-based external storage boxes feature 3.5" disk drives. The IBM EXP3000 deploys a single RAID controller and twelve SAS drives in a 2u shelf, giving it the capability to pack almost 4TB in the configuration. Though SAS drives are available in both 2.5" and 3.5", most in the industry agree that 2.5" SAS drives will primarily reside in performance-centric enterprise servers and not external arrays since the smaller size means less capacity per unit. This allows for maximum capacity as storage needs expand. Meanwhile, expect value-based servers to adopt 3.5" SAS drives in order to save cost.

Authors: Michael Sebesta and Joseph Rebrovich
System Integration Test Lab
Hitachi Global Storage Technologies

Serial Attached SCSI (SAS) is a new serial interface for enterprise hard disk drives that will eventually replace aging parallel SCSI technology. The new serial interface provides much higher data transfer rates, improved scalability and superior reliability. SAS is also compatible with Serial ATA (SATA), which has become increasingly popular for use in nearline and entry-server applications. The SAS architecture allows IT managers to deploy either high-performance SAS or cost-effective SATA drives in the same storage enclosure, providing unprecedented design flexibility for server and storage subsystem deployments.

New storage interconnects can often present system integration challenges. SAS is no exception, although SAS' unique development approach has, in many ways, helped to minimize the challenges.

Author: Jim Pascoe, Hitachi Global Storage Technologies

Data center workloads have increased exponentially in recent years, requiring IT managers to find new ways of scaling their enterprise storage resources in a manner that is both highly reliable and cost-effective. With the introduction of complementary serial interface technologies, IT managers now have the flexibility to deploy either high performance Serial Attached SCSI (SAS) drives or cost-effective Serial ATA (SATA) drives in a SAS storage environment. Hardware compatibility between the new interfaces will provide unprecedented design flexibility for server and storage subsystem deployments.

SAS was designed to be the successor to parallel SCSI, which has been used effectively as an enterprise storage interface for more than 20 years. Maintaining compatibility with the last 20 years of application software investment, SAS supports the SCSI command set and protocol. SAS will support faster data transfer rates and more devices per controller, as well as reduce the size and complexity of the cables and connectors (thus enabling smaller, more densely-packed disk arrays).

Author: Sam Sawyer
Hitachi GST

The new serial interfaces, Serial Attached SCSI (SAS) and Serial ATA (SATA), have been designed to replace their parallel predecessors. They will support faster data transfer rates and more devices per controller, as well as reduce the size and complexity of the cables and connectors (thus enabling smaller, more densely-packed disk arrays). System builders will also be able to integrate SAS and SATA hard drives in a single enclosure.

SAS goes beyond SATA by adding dual porting, full duplex and device addressing; furthermore, it offers higher reliability, performance and data availability services, as well as logical SCSI compatibility. SAS will continue to enhance these and other metrics as the specification evolves, including increased device support and longer cabling distances.

Author: Marty Czekalski
Maxtor Corporation

When introducing a new interface into a system, several questions generally come to mind such as; what characteristics does the new device possess, what are its specifications and how will it fit into the overall system design?

This development overview article will look at devices that can be used in Serial Attached SCSI (SAS) systems. We will also look at some of these devices' characteristics and how various standards organizations and committees manage their specifications. Finally, we will talk about where a designer or technical professional can go to get additional information on various components. (For the purposes of this article we will focus primarily on SAS disk drives and will briefly discuss tape drives and Serial ATA (SATA) disk drives.)

Jim Pascoe
Hitachi Global Storage Technologies

Use of the parallel bus interface, which has long been the industry-standard storage interconnect, is on the verge of decline among the vast majority of system builders. Components that are based on the aging interface are increasingly being replaced by their evolved serial counterparts—Serial Attached SCSI (SAS) and Serial ATA (SATA).

The new serial interfaces are designed to address the bandwidth limitations of their predecessors. They will support faster data transfer rates and more devices per controller, as well as reduce the size and complexity of the cables and connectors (thus enabling smaller, more densely-packed disk arrays). Among the most significant benefits is that incompatibility between SCSI and ATA will finally be addressed.