Delivering on the Promise of SAS

Author: Todd Mottershead, Manager, ProLiant Server Development

With virtually every IT department in today’s corporate world facing growing user demands and shrinking budgets, storage vendors are rushing to deliver the cost efficiency of low-end systems with value-added features and availability levels typically found only in enterprise class facilities. This focused effort began back in 2005 when companies like HP were faced with technical hurdles ranging from drive density limitation (approximately 300 GB) to storage interface challenges (Ultra 320 was running out of steam), to seemingly simple issues like bulky parallel SCSI cables, not to mention the demands of the customer.

The concept of a “challenge” with changing customer usage models was an understatement. Real end-user needs were shifting. Not only was computing infrastructure performance important but exponential demands for new storage facilities driven by legislative requirements including Sarbanes-Oxley and others were being felt at every level of the customer tier structure. And, for the first time in memory, the costs of technology acquisition fell below that of ongoing operational and maintenance costs (see Figure 1).


Figure 1: (Overall Cost of Storage Ownership – Source: HP)


In addition, further customer dialogue on overall system efficiencies led HP to seriously consider technology alternatives to address needs that once were considered simple: power and space.

It was not an option to tell a customer either, “We can reduce your density to maintain cost parity” or “you can wait for a better solution next year.” We did find, however, that it was palatable to show our customers how to leverage their existing storage infrastructure technology (SCSI) while enabling improved business efficiency.

Fortunately, the larger storage industry recognized the very same challenges as we did at HP and starting thinking about technology solutions that could ease customer pain and provide better returns on overall investment.

Along came SAS.

Not only were things like cabling grossly simplified but also domain sizes were substantially larger (no more parallel SCSI device limitations), allowing for system configurations viewed previously as impossible or unbelievably expensive. For the first time with a new storage technology it was possible (and economical) to deliver “amazing” amounts of storage for the end-customer. (See Figure 2)


Figure 2: (16 channel controllers, 108 spindles/slot, 32.4TB per slot)


Of course, with the advent of SFF (small form factor) we addressed not only density requirements but also power and space savings.

Industry leaders are often asked, “Are we delivering on the promise of SAS?” – I say so and here’s why:

  • SAS leverages the proven SCSI technologies (hardware and software) that customers expect in data center environments, providing robust solutions and generational consistency. Since it is based on a serial interface, it provides for increased device support and bandwidth scalability, while reducing the overhead impact that challenges today’s parallel SCSI environments. It also leverages SATA development work on smaller cables and connectors — providing customers a downstream compatibility with desktop class ATA technologies.
  • End-user benefits include enterprise class robustness, investment protection in compatible SCSI software and a choice of direct-attach storage devices (SAS or SATA) driven by the economics of a particular application set. In addition, longer cabling distances, smaller form factors and greater addressability lead to greater flexibility when deploying mainstream data center servers and subsystems.
  • Finally, the industry-leading legacy of SCSI reliability and peace of mind will satisfy user needs for continuity in the data center.

When these elements are combined, it’s obvious that our industry is delivering on the promises made to our customers.

How can SAS benefit you?

  • Customer drive choices (SAS/SATA)
  • Legacy Compatibility
  • High Performance
  • Scalability
  • Future Proof
  • Delivers Value Today!

The storage industry has met the challenge of rapidly and successfully addressing the changed customer usage models of a few years ago. The best of SCSI was retained, including backward compatibility with Ultra320, SATA drives were integrated into SAS-based systems, smaller cables and connectors greatly reduced the cost of infrastructure and operation as the cooling requirements were reduced. As a result, the industry is rapidly realizing the promise of SAS.

Todd Mottershead manages the team responsible for the HP SmartArray family of SAS and SCSI optimized solutions. With his teams innovation in areas such as Data Protection and Scalable Storage solutions, HP is uniquely positioned to deliver storage and server solutions that combine leading edge performance with unmatched reliability.

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