Authors: Harry Mason, President of STA and Alice Tate, STA Marketing Manager
Special thanks to John Lohmeyer, Chair of the T10 Committee and Marty Czekalski, Vice President of STA, for their contributions
T10 is a Technical Committee of the InterNational Committee on Information Technology Standards (INCITS, pronounced “insights”) and develops standards so that features and benefits can be implemented in commercial products in a common, compatible manner. INCITS is accredited by, and operates under rules that are approved by, the American National Standards Institute (ANSI). These rules are designed to ensure that voluntary standards are developed through the consensus of industry groups. Serial Attached SCSI (SAS) becomes a standard through the work, commitment and dedication of the T10 Committee members.
STA and T10
The SCSI Trade Association (STA) is not responsible for the technical standards concerning the SAS specifications. However, STA and the T10 Committee have a close working relationship. STA and T10 meetings are co-located to enhance the communications between, and the cooperation of, the two organizations. STA focuses on identifying SAS’ marketing requirements and provides the forum to reach a consensus on features and benefits found on the roadmap. STA’s primary mission is to promote the understanding and use of SAS technology. To that end, we are writing this article to further the industry’s understanding of how SAS becomes a standard.
Defined Procedures and Policies
The T10 Committee has a clear set of procedures that guide the emergence of new standards. STA has developed a roadmap that maps SAS technology through 2015, however it is incumbent on the T10 Committee to propose new projects for each new SAS generation, and then develop a set of standard documents which support each generation.
Why SAS for Nearline?
While it may be tempting to focus on the significant performance advantages that Tier 2 nearline SAS drives offer over SATA drives, the more essential benefit to most IT operations is the superior data integrity and reliability that define 6Gb/s SAS storage solutions.
Table 1: SAS/SCSI Nomenclature Table
As we transition from one generation to the next, STA hosts evening meetings during T10 week to reconcile our vision of the market with the best technical proposals on what subsequent generations of the technology should become. Company representatives give presentations suggesting various features and technology options, along with lively discussions which expose the most desirable features. Once consensus is reached, T10 writes and approves a Project Proposal, which then goes to INCITS for their approval. This step takes only a few weeks. The new project then goes through a development process that can take years to create. Once development is complete, the project goes through an approval process to ensure broad industry support. This step usually takes about six months.
Figure 1: INCITS / T10 Standards Approval Process (Simplified)
The Process is as Follows with Defined Comment and Reaction Periods within Each Step:
- Project proposal
- Development phase
- T10 Letter Ballot (30 days)
- Forward revised draft to INCITS for public review (45 days)
- INCITS Management Review
- INCITS Letter Ballot (30 days)
- ANSI Board of Standards Review
- ANSI Publication Phase
- Standard Published
The process outlined above is simplified considerably for the purpose of clarity in this article. For example, during the comment periods, draft changes could include anything from correction of an editorial error (which is called non-substantive) to making a technical change (which causes the draft standard to iterate back through the approval process, potentially adding months to the schedule).
SAS-2, the draft technical specification on which 6Gb/s SAS is based (see Table 1 above), is currently in step 6, the INCITS Letter Ballot. 6Gb/s SAS requires the 6Gb/s transfer rate, Standardized Expander Zoning, Expander Self-Discovery, Spread Spectrum Clocking, the use of Mini-SAS connectors and if Multiplexing is implemented, it must be implemented as defined in the SAS-2 draft technical specification.
Developing SAS Products
In a perfect world, everyone would wait until the standards are complete and approved before beginning product development. Truthfully, in order to remain competitive, companies must start product development in conjunction with the standards development process. For example, as stated earlier, SAS-2 has not fully completed the standards approval process. However, complete 6Gb/s SAS systems have begun shipping and STA member companies are currently in the early stages of ramping to volume production. STA held its first 6Gb/s SAS plugfest in November 2008, with seventeen companies present (see http://www.scsita.org/news_events/dirReleases/scsi081124.html for more information).
These plugfests greatly reduce the risk of introducing new technologies prematurely and go a long way in hardening the upcoming product generations prior to broad market adoption.
Many STA member companies have announced 6Gb/s SAS product releases, live demonstrations at industry events, and partnerships around 6Gb/s SAS (see STA member press releases at: http://www.scsita.org/news_events/pressReleases.html).
Summary
The standards process is a healthy and collaborative industry development that involves T10 – the formal standards organization, as well as STA – the industry trade association, jointly focusing on the goal of developing rich SAS capabilities within a framework of interoperability.
For More Information
Please visit the T10 Committee site (http://www.t10.org/ for the most comprehensive location of past and present documents on the technical specifications for SAS.
You can also find the detailed rules that T10 must follow at: INCITS RD-1, Policies and Guidelines http://www.incits.org/rd1/INCITS_RD1.pdf and
INCITS RD-2, Organization and Procedures http://www.incits.org/rd2/in081453.pdf
