SAS Evolves with Changing Enterprise Storage Needs

It’s nothing new that technology changes rapidly. Enterprise storage is no exception. Keeping data moving at faster speeds and having the ability to properly manage that data has never been more critical to having businesses run smoothly. Applications such as database, commerce and transaction, web serving and streaming use massive amounts of data and storage requirements continue to increase. New technologies need to be integrated into these storage architectures to reduce potential bottlenecks.

12Gb/s SAS as well as 6Gbs/ SAS HDDs, SAS and SATA SSDs, SAS plumbing, optical and copper managed cables, and new Mini-SAS HD , are all examples of technology advancements that create tangible benefits to data hungry applications and reduce total cost of ownership (TCO), while increasing performance.

6Gb/s SAS is the standard for high-performance, enterprise storage. Most storage device manufacturers offer 6Gb/s SAS as their performance option. High performance HDDs and storage arrays benefit from 6Gb/s SAS, but SSDs can best take advantage of the bandwidth provided by 6Gb/s SAS.

What makes 6Gb/s SAS best for evolving enterprise storage?

SAS has always been defined for enterprise data within servers and external storage. The SAS roadmap is managed by storage and computing companies that service enterprise businesses, as well as small and medium businesses. The SAS roadmap (Figure 1) shows regular intervals, introducing new features and speeds for server and storage designers to understand, architect and deploy the new technology in a manageable timeline, allowing for the entire industry and customers to align with the new standard.

Figure 1 — SCSI Trade Association SAS Roadmap as of Q1 2011

Each generation innovates with faster speeds, but managing enterprise data has become increasingly important, and in many cases, critical to the success of the company.

Longer Cables and Improved Manageability
SAS capabilities are extending further as a storage fabric and now offer active options up to 100 meters in length for storage SANs and data centers. Additionally, actively managing the cables has been made possible with smarter cables and connectors that will eventually communicate with some storage management tools.

The first generation of SAS at 3Gb/s specified cables are up to three meters in length. As SAS gained momentum, 6Gb/s SAS defined a maximum cable length of six meters, which was sufficient for inside the server and close range connectivity between servers and storage chassis and/or SAS switches. Scalability increases with longer cables and enables larger and more complex box-to-box and rack-to-rack connections.

The SAS Advanced Connectivity Roadmap (Figure 3) shows the cable lengths (Y-axis) appearing with the different generations of SAS (X-axis). The overlapping boxes contain the connector type and standards name (SFF number). Mini-SAS is the most common connector for today’s 6Gb/s SAS implementations offering 10-meter connectivity, internally with SFF-8087 and externally with SFF-8088. Mini-SAS Active Copper uses the same SFF-8088 connector but with an active connection, extending the reach up to 20 meters.

To continue the scalability of SAS, the Mini-SAS HD (high-density) connector is available for 6Gb/s SAS and will become the standard for cabling for 12Gb/s SAS connections outside the server. 12Gb/s SAS connections inside the server may still use the tried-and-true Mini-SAS connection, but as the Mini-SAS HD becomes more widely used and performance demands and smaller server form factors continue to evolve, the HD connectors will eventually become the norm.

Figure 2 — Comparison of Mini-SAS and Mini-SAS HD cabling

Aside from the longer reaches of SAS connectivity, managing connections between storage, servers and switches becomes increasingly important. The ability to view the status of active and passive connections, and be alerted if there is a connection problem is valuable insight for the IT manager when troubleshooting a storage problem. SAS Connectivity Management provides this insight with technology built into the cable/connector. IT managers will be able to perform remote discovery, diagnose individual connections, and quickly isolate faults to make repairs. This improves the overall TCO of a SAS-based storage system.

Figure 3 — SAS Advanced Connectivity Roadmap

The SAS Advanced Connectivity Roadmap was designed to support larger scaled and tiered architecture to accommodate greater numbers of drives and storage subsystems, as well as improving the overall availability, manageability and flexibility of SAS deployments. With convergence on the Mini-SAS HD connector over the next few years, inventory management will be simplified as well. Electronically keyed connectors and backward compatibility also reduce the number of different cable types required in a given system, again reducing the cost of owning and managing the system.

Applications Drive the Architecture
The “cloud” and associated applications are driving scale-out computing architecture, including much more storage to service applications such as Facebook, Google Docs, Twitter, on-line business and consumer storage. The list goes on. The need for more storage is there, and more intelligent storage is required to service these growing applications. Many of these systems consist of a large number of servers and associated storage, which are all interconnected. When there is a node failure, the server or storage node is simply replaced. When millions of users are potentially accessing data through that node, a failure, even for a short time, can impact a lot of people. It is critical for an IT manager to quickly identify, diagnose and replace the failed node.

SAS and SCSI specifications have always evolved to address current and future server and storage requirements. The storage protocols continue to evolve in conjunction with applications and the demands placed on server and storage architectures. SAS evolves to address performance needs by doubling the speed each generation, with additional innovations developed to address architectural and system management needs that arise from new demanding applications. SAS Advanced Connectivity meets these demands today and will extend into future generations. Stay tuned to the advancements of SAS to gain insight into the evolution of storage.

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