If you're a regular reader of STA's Serial Storage Wire, you know that there's a transition taking place in the storage industry from FC-AL to Serial-Attached SCSI (SAS) storage architectures and disk drives... NetApp is well into this technology transition, where SAS-connected disk shelves now account for a majority of storage shipped with new NetApp® systems.
SAS Library » 3Gb/s SAS: 2011
The first generation, 3Gb/s SAS, replaces parallel SCSI which could no longer keep pace with industry performance and scalability demands. SAS fulfilled the storage industry's need for faster systems with more advanced capabilities. SAS features which support faster performance include dual-port drives and wide ports, enabling full-duplex data transmission plus aggregated bandwidth. Universal connectivity is an added SAS advantage.
The industry is gearing up for Serial Attached SCSI (SAS), a new, faster version of SCSI designed to meet the demands of enterprise IT for the coming decade. The SAS interface supports both SAS disk drives for mission critical applications and Serial ATA (SATA) drives for low-cost bulk storage of reference data, giving IT managers greater price and performance flexibility in their storage strategies. As a result, managers can now make storage decisions that better align with business requirements, balancing their storage investment between compatible technologies and assigning storage devices to data based on the information's business value, providing a more cost-effective solution. (By Enterprise Management Associates, November 2004)
SAS General Overview - 1.3MB
General marketing background, followed by the key topics from each layer.
The Serial Attached SCSI logo was created by the SCSI Trade Association (STA) membership to facilitate the identification of the Serial Attached SCSI architecture in the market place.
STA has not established a trademark or product compliance program to be associated with the logo. STA assumes those using the logo will do so in a manner that accurately depicts conformance with the Serial Attached SCSI specifications promulgated by the T10 Committee. STA expects that the market will use the Serial Attached SCSI logo as it has made use of the term "SCSI" as well as the various graphical and iconic representations of that standard. to be verified
In this regard this style guide has been prepared to encourage a consistent use of the logo to build a voluntary brand identity for this new and important interface.
The base design is a two-color logo in a borderless rectangle as shown below. There is also an "icon" version of this logo. The logo and icon may only be reproduced in the established two-color version or in black and gray-scale. Please refer to SAS Style Guide for more information about usage of the SAS logo and icon.
The various options are all available in .eps, .tif and .jpg formats for both color and black and gray-scale versions. Each .zip file below contains each of the 3 formats for the version displayed:
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Serial Attached SCSI Cables and Connectors
In the process of defining and standardizing the Serial Attached SCSI technology, the T10 technical and SFF committees have defined cables and connectors to support the many different SAS-based system topologies that can now be developed. These cables and connectors are available today from many suppliers. Additional connectors are also in development that will provide higher I/O density. This white paper summarizes these solutions and provides direction for the connectivity implementation of SAS-based systems. (February 2005)
SAS Architecture - 348KB
Covers the SAS object model, physical links and phys, ports, SAS devices, expander devices, domains, edge expander device sets, pathways, connections, SAS address, reset sequences, state machines, transmit data path, and describes the expander device model.
SAS Raid-On-A-Motherboard: Affordable, high performance RAID
Full-featured RAID data protection is becoming a standard feature in businesses of almost any size, thanks to the increasing affordability of implementing RAID technology. Cost-effective RAID-on-motherboard (ROMB) solutions, using integrated RAID-on-Chip (RoC) devices, enable system integrators to implement robust hardware RAID solutions while optimizing their server motherboard investments. With the union of high-security, cost-effective ROMB and the built-in reliability and availability features included with SAS, system IT managers can now meet the data security requirements of tomorrow on the restrictive budgets of today. (April 2005)
SAS Physical Layer - 256KB
Describes the lowest layer of SAS, covering passive interconnects (cables and connectors) and electrical characteristics.
Managing Access Control Through SAS Zoning
Serial Attached SCSI (SAS) is gaining popularity in small storage area network (SAN) server environments. With its rise in popularity comes the need to segregate and manage device traffic in a similar fashion to what is already done in larger Fibre Channel networks by using zones or in Ethernet using virtual LANs. By doing this, IT administrators can create much more flexible, scalable, and efficient server networks that meet their business needs. SAS zoning, a proposal to the T10 Technical Committee for inclusion in the SAS-2 specification, provides this capability. (September 2005)
SAS Phy Layer - 256KB
Describes 8b10b coding, OOB signaling, and speed negotiation.
SAS Link Layer - Part 1 - 364 BK
Covers primitives, clock skew management, CRC, scrambling, bit order, address frames, identification and hard reset sequences, and connections.
SOptimizing Storage with SAS: Seize the 15K Advantage
Enterprise storage is entering a new era of cost-effectiveness and efficiency, driven by the growing movement towards specialized storage solutions. The value proposition of this application-focused storage is straightforward: Optimize price/performance by matching the storage device to the specific characteristics (quantity, needed availability, etc.) of the data. Naturally, such an approach requires multiple device types, each cost-effectively performing its respective storage duties. (April 2006)
- Welcome Introduction (Harry Mason, LSI & STA)
- SAS Market Update (Mike Karp, EMA)
- Delivering on the Promise of SAS (Todd Mottershead, HP)
- SAS To The Rescue (Arlin Sorenson, Heartland Technology Solutions)
- SAS: Improving Performance, Lowering Cost (Bob Griswold, Microsoft)
- SAS Powers Ahead! (Marty Czekalski, Seagate & STA)
SAS Link Layer Part 2 - 344 BK
Covers arbitration fairness, deadlocks and livelocks, rate matching, SSP (Serial SCSI Protocol) frame transmission, STP (Serial ATA Tunneling Protocol) and Serial ATA frame transmission, and SMP (Serial Management Protocol) frame transmission.
Over the past several years, companies have enjoyed a wide selection of technologies within the enterprise disk array market. Serial ATA (SATA), Fibre Channel (FC), and even parallel SCSI are viable options. More recently, Serial Attached SCSI (SAS) has entered the mainstream enterprise-class storage market, and its share is growing rapidly. Gartner Dataquest expects SAS to grow from its current 8 percent market share in multi-user drive shipments to 16 percent in 2007. By 2009, analysts expect SAS to make up 45 percent of that market. (March 2007)
- Welcome & Introduction to SAS (Marty Czekalski, Maxtor)
- Impact of SAS on Storage (Phil Brace, LSI Logic)
- Transitioning the Market to SAS (Bob Moore, HP)
- Database Server Bricks: Case Study (Rich Johnson, Microsoft)
- Demo Preview & Questions (Harry Mason, LSI Logic)
March 2005 IDF Storage Community Presentation, by Marty Czekalski
- SAS Products Entering the Market
- SAS Advantages
- SAS System Features
- SAS Protocol is the Key to System Communication
- Typical SAS High Availability System
Steve Denegri, RBC — Predicts
"Serial Attached SCSI (SAS) is poised for adoption as a data transport in addition to its usage as a disk interface. In fact, with direct-attach storage (DAS) remaining a popular choice for incremental disk capacity needs, a tremendous opportunity exists for SAS in connecting these storage resources to servers. Just as SAS will likely displace Parallel SCSI as the interface of choice for enterprise disk drives, a similar upgrade to SAS may also take place at the host-attach level."
SAS SCSI Upper Layers - 308 BK
Covers SCSI standards organization, basic SCSI architecture, important SCSI commands and status codes, important task management functions, SCSI transport protocol services, the SSP (Serial SCSI Protocol) transport layer, SAS-specific mode pages, SAS-specific log pages, and power conditions/spinup controls.
SAS Starter Kit: Mixing SAS and SATA Drives in a Single Enclosure
Serial Attached SCSI (SAS) has begun to play a key role as the enterprise continues to move towards more optimized, cost-effective storage platforms. Overcoming many of the limitations of traditional parallel SCSI implementations, SAS solutions that offer connectivity choices and support both SAS and Serial ATA (SATA) drive technology enable enterprises to easily create tiered storage environments. However, concerns about performance expectations and Rotational Vibration Interference (RVI) in mixed SAS/SATA environments are preventing many organizations from adopting SAS technology. (March 2007)
SAS ATA Upper Layers- 228 BK
Covers basic ATA architecture, the ATA task file, ATA commands, Serial ATA frames, and compares ATAPI (ATA Packet Interface) vs. native SCSI.
The first generation, 3Gb/s SAS, replaces parallel SCSI which could no longer keep pace with industry performance and scalability demands. SAS fulfilled the storage industry's need for faster systems with more advanced capabilities. SAS features which support faster performance include dual-port drives and wide ports, enabling full-duplex data transmission plus aggregated bandwidth. Universal connectivity is an added SAS advantage.
Optimizie Your Investment with Serial Attached SCSI (SAS)
Since the emergence of Serial Attached SCSI two years ago, many high-end storage solution providers and OEMs have recognized the advantages of SAS over its parallel predecessor. Vertical markets that have since adopted SAS technology are the entertainment industry, medical imaging, financial institutions and research and government institutions, which typically need performance and/or capacity. SAS can offer good value, performance, and scalability. (October 2007)
Overview of SAS architecture and position in the market; by: Marty Czekalski, Technical Marketing Manager, Maxtor — Member of the Board and Vice President of SCSI Trade Association.
- Serial Attached SCSI is the next evolution of SCSI beyond U320
- SAS has been designed to be a device and near cabinet interface only, not a network interface
- Leverages an enhanced Serial ATA PHY while adding support for a second port
- Serial SCSI utilizes features of Fibre Channel AND compatibility with SATA drives in a point-to-point, switched architecture
SAS Management Upper Layers and Port Layer - 208KB
Covers the SMP transport layer and all the SMP functions, and concludes with a look at the port layer (which ties the transport layers to the link layers).
What is Serial Technology?
Data travels in time and space between system components--the server and PC, the PC and connected devices, and within the software. Data that is transferred serially moves one bit at a time in linear succession through a fast single path. In contrast, data transferred in parallel mode consists of many data bits moving together simultaneously on a shared pathway.
The primary differentiator between serial and parallel architectures is the clock. In serial technology the clock is embedded in the data. This results in data constantly moving through the system from one point to another using the bandwidth to the fullest extent. A parallel architecture clock moves data at a measured pace, resulting in intermittent periods of inactivity. Data using parallel paths is akin to a vast army marching under the command of one general--it simply can't move as fast. The benefits of serial technology are well understood and are now being used for the most advanced desktop and enterprise applications including USB, 1394, Ethernet and Fibre Channel.
SAS_FCP_comparison_public.pdf - 116KB
Covers the SMP transport layer and all the SMP functions, and concludes with a look at the port layer (which ties the transport layers to the link layers).
- Serial Attached SCSI 1.0 Features
- Press Quotes
- INCITS Specification Schedule
- Serial Attached SCSI Deployment
SAS Quiz Questions - 76KB
SAS Quiz Answers - 86KB
A few fill-in-the-blank slides that review some key concepts.
- Key Serial Attached SCSI Features
- Serial Attached SCSI Topology
- Multiple Pathways Allow Concurrent Operation
- Maximum Expander Device Topology
- Two Edge Expanders
- Typical Serial Attached SCSI Configuration
- Out of Band Signaling (OOB)
- Serial Attached SCSI Expander Operation (with SAS drives)
- Serial Attached SCSI Expander Operation (with SATA drives)
- Serial ATA Command Queuing and Serial Attached SCSI
- Enabling Future Compatibility
