STA

Author: Alvin Ooi, Marketing Manager,
AIC/Xtore

Since the market 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.

SAS Advantages

In general, everyone recognizes the following advantages SAS offers:

• Superior aggregated performance over 4-lane wide ports -- providing throughput of up to 12Gb/s SAS
• Dual-ported design with fail-over capabilities
• Support for both SAS and Serial ATA (SATA) HDD in a single enclosure to eliminate redundant qualification and certification efforts, as well as the ability to achieve cost-effective storage
• Available edge and fan-out expander technologies for easier expansion and unmatched scalability
• Longer interconnect distance allowed compared to SATA for low-cost expansion enclosure solutions

Although overall market share is still relatively small compared to SATA, parallel SCSI and even Fiber-Channel, the majority of the next generation solutions currently being designed by OEMs are based on SAS technology. But demand for SAS is high and increasing.

Author: Levi Norman, ISS Storage Strategist, Industry Standard Servers
HP

From the time SAS was envisioned to this point, we have heard time and again it is to be much more than parallel SCSI ever hoped to be. It should deliver unsurpassed ROI, new and unique configurations and unparalleled performance gains, etc. It actually began as an engineering dilemma of how to overcome the issue of speeding up the bus and keeping all the data synchronized, on path, and ready to arrive at its destination in a timely and safe manner. pSCSI could no longer guarantee the safety or even the timely arrival of the 'payload,' thus the look elsewhere for a competent answer.

The idea of serial technology has been around for quite some time in varying forms and formats, alongside varying speeds and levels of security and connectivity. But the idea of using it cost-effectively outside of the Fibre Channel world with a cost-effective connection, (although smaller, stronger connectors, thanks to IB and ATA), had only recently been thought of. Long story short, SAS was born. It was born with 3Gb speeds, it was born with great expandability above and beyond pSCSI, and it is born with better inherent management than pSCSI.

ROI on a data center is easily calculated, right? Yes, if you are starting from the ground up. What about those folks that have a datacenter today? What do they do? How do they realize an immediate benefit? How do they calculate it? First, SAS is inherently SCSI and inherently connects into the architecture, yet immediately has architectural and performance benefits. The drives became more robust as they became smaller, point-to-point architectures sped up the transactions, and scalability went up nearly tenfold. Results get better immediately for even the existing datacenter. And secondly, HP as a company, offers a host of methods to measure performance and transactions with a variety of tools and industry monitored tests.

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.