STA

Author: Mark Peters, Storage Systems Analyst, and Tony Palmer, Lab Engineer
Enterprise Strategy Group

Introduction
The relative success of new technologies is not a one-way street. Indeed, the history of IT is littered with great developments that never 'made it', storage technologies that have had more written about them than on them. 6Gb/s SAS products look great, and full of value, but will the enthusiasm of its promoters be matched by an eagerness to invest from its potential users? With the 6GB/s products rolling out now and over the coming months, there are many Enterprise buyers trying to figure out if, and how far, to jump into SAS. ESG has looked at this from both sides - the technical suitability as well as the adoption logic - and expects that SAS will indeed find success in Enterprise environments.

This article is not intended to repeat in any detail all the well-known attributes of SAS. Yes, it offers a number of benefits compared to traditional parallel SCSI technology including the use of thinner cables, the ability to transfer data over longer distances, providing faster data transfer rates, and the ability to create storage area networks; new and improved capabilities in terms of scalability, performance, capacity, zoning, multiplexing, security and so on, all look great on paper...but is SAS appropriate for and ready for the Enterprise? And is the Enterprise ready for SAS?

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: John Rydning, Research Director, Hard Disk Drives
IDC

Storage device options continue to broaden for disk storage system OEMs and end users. For enterprise applications, hard-disk drives (HDDs) are now available in several form factors, configured with parallel SCSI, Fibre Channel, Serial ATA (SATA) or Serial Attached SCSI (SAS) interfaces. An increasing number of solid state drives (SSDs) are now also shipping for enterprise applications. DRAM-based SSDs have for many years satisfied the needs of very high performance, latency-sensitive environments, but at a high cost. Now, with the price decline in NAND flash and advances in technology, NAND-based SSDs have a growing opportunity in the datacenter. Similar to HDDs, flash-based SSDs are offered with several interface options.

Today's diversity of storage device options for the datacenter contrasts sharply with the limited selection available just five years ago. Consider the changes that have taken place just with hard disk drives. In 2003, essentially two HDD form factors serviced the large percentage of enterprise datacenter storage demands: 3.5 inch 10,000 rpm and 3.5 inch 15,000 rpm HDDs. Today, in addition to these 3.5 inch enterprise class products, the HDD industry also ships 2.5 inch 10,000 and 15,000 rpm enterprise-class small-form-factor (SFF) drives. Collectively, IDC classifies these drives as performance-optimized HDDs. By 2009, 2.5 inch performance-optimized HDDs will out-ship 3.5 inch products.

Author: Mike Karp, Senior Analyst,
Enterprise Management Associates

"Storage density" is the term that describes how much storage capacity can be packed into a specified amount of space. The actual measurement varies a bit depending on your focus. Disk drive vendors measure bits per square inch, while tape vendors think in terms of bits per linear inch. Data center managers measure things at a more macro level: for them storage density is a measure of terabytes (and increasingly, petabytes) per square foot of floor space.

At least that's the way things were measured up until recently.

Author: Ashish Nadkarni, Principal Consultant
GlassHouse Technologies

Flash drives, also known as solid state drives, have a promising future in the enterprise space. They promise to overcome literally all limitations of traditional hard drives - power consumption, heat dissipation, mean time between failures, speed and IO/s, etc. The list is long. There is no doubt that eventually they will replace all rotational hard drives in the enterprise space, as well as the consumer market. If you have bought into the promise of solid state drives and are planning to invest in it right away, hold your plans for now. The technology should be continually researched to figure out how to best help your environment, stopping short of actually buying anything - yet. The technology is seemingly mature but still has to establish itself in the enterprise space. Then, and only then, will it become viable as a replacement technology for spindle-based drives.

Author: Sam Barnett, Business Manager, Serial Attached SCSI and Serial ATA Storage / Storage Networking Products, Storage Products Group, Maxim Integrated Products

As first generation systems based on Serial Attached SCSI (SAS) technology enter the market, leading server and storage OEMs are racing to deliver the next group of platforms based on an ever-evolving technology landscape. Unlike other semiconductor vendors, Maxim opted to enhance its popular NexSAS™ product family concurrently with the release of generation I systems. This leapfrogging approach to the deployment of SAS technology has led to the introduction of many new products with features found only in high availability, superior performing Fibre Channel systems today. Comprised of three new high-phy-count expanders, extensions in intelligent mux/de-mux devices, a new enclosure management/SAS backplane controller, and the industry's best rate, agile signal conditioners, the NexSAS™ line delivers on the promise of high performance storage solutions for SMB (small/medium business) as well as enterprise systems.

The Maxim NexSAS™ product family is divided into four functional areas: expander technology, SAS/Serial ATA (SATA) support devices, server/enclosure/baseboard management, and signal conditioning. This article explores Generation 1.5 NexSAS™ expander technology in detail.

Excerpted by David Reinsel, Director, Storage Hardware Research,
IDC
Note: The following is an excerpt from an IDC publication¹

Hard disk drive (HDD) interface transitions within enterprise systems are being clouded by a number of issues. Disk storage system vendor strategies are far from similar and HDD vendors are considering various options with respect to interface technology transitions. One thing is certain: end users will not tolerate a digression from today's performance and reliability. Moreover, they expect to see cost per gigabyte continue to drop.

As the parallel SCSI HDD interface finishes its longstanding run for over 20 years, a relatively new interface, Serial Attached SCSI (SAS), is prepared to take the baton. The difficulties of extending the legacy parallel SCSI interface are well-known, and SAS is being greeted with open arms. SAS drives have been available since 2004, but 'real' shipments started in 2005. Over 3.7 million SAS HDDs shipped worldwide from 2005 through 2006.

Author: Sam Barnett, Product Line Manager, Serial Attached SCSI and Serial ATA Storage & Storage Networking Products, Storage Products Division,
Vitesse Semiconductor

As first generation systems based on Serial Attached SCSI (SAS) technology enter the market, leading server and storage OEMs are racing to deliver the next group of platforms based on an ever-evolving technology landscape. Vitesse opted to enhance its popular NexSAS™ product family concurrent with the release of generation 1 systems. This leap-frogging approach to the deployment of SAS technology has led to the introduction of many new products with features found only in high availability, superior performing, Fibre Channel systems today. Comprised of three new high-PHY-count expanders, two new RAID-on-CHIP offerings, extensions in intelligent mux/de-mux devices, a new enclosure management/SAS backplane controller, and high-rate, agile signal conditioners, the NexSAS™ line delivers on the promise of high-performance storage solutions for SMB (small/medium business) as well as enterprise systems.

Author: Sam Barnett, Product Line Manager, Serial Attached SCSI
and Serial ATA Storage & Storage Networking Products, Storage Products Division,
Vitesse Semiconductor

Serial Attached SCSI (SAS) offers a wealth of benefits to the enterprise server and enclosure customer (high reliability and performance, mixed enterprise/desktop drive support, improved economies of scale), and key to scalability and performance is the expander.

This article offers a brief technical exploration of SAS expander technology and its potential evolution into the "interconnect-fabric" of choice for midrange and enterprise storage systems of tomorrow.

The author assumes the reader has some knowledge of point-to-point storage architectures and SAS nomenclature. Detailed specification information on SAS can be found on the T10 website under http://www.t10.org/ (click "Drafts" then "Serial Attached SCSI (SAS)" under "Protocols and Physical Layers"). Similarly, the SCSI Trade Association (STA) also offers a robust set of tutorials on SAS. The reader may reference this material at http://www.scsita.org.

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).

Serial Attached SCSI (SAS), the next generation SCSI standard, provides IT implementers with maximum flexibility in configuring their storage environments. SAS supports logical compatibility with Serial ATA (SATA), enabling one storage design to service both high performance mission-critical storage (SAS) and low cost bulk storage (SATA).

PMC-Sierra recently spoke with members of IT departments at medical imaging, software development and financial companies to discuss their current storage strategies and their thoughts on the benefits that SAS can provide. Their responses (summarized below) highlight the exceptional flexibility and cost-effectiveness that SAS/SATA compatibility can bring to the enterprise.