Three Steps Forward, No Steps Back: Investment Protection with Serial Attached SCSI

Never before has the enterprise enjoyed such a broad variety of storage solutions from which to choose. Innovative new offerings in both hardware and software seem to appear almost daily, promising unprecedented flexibility to specify the most appropriate, targeted solution for any storage challenge.

Yet in the midst of this embarrassment of riches, IT budgets continue to undergo close scrutiny, leading prudent managers to view untested new solutions with a cautious eye. Indeed, more than a few veteran IT professionals have been known to instinctively flinch at the phrase “technology breakthrough.” Why? Not because they eschew technical progress (far from it), but simply because hard-earned experience has shown them that deploying fundamentally unfamiliar solutions can be a “two steps forward, one step back” proposition.

That is, many of the gains offered by a new hardware or software solution can be initially offset by the time and expense needed to integrate it into the current computing environment–including modification or replacement of existing infrastructure, and retraining IT personnel to deploy, maintain and troubleshoot the unfamiliar solution. Downtime and diminished productivity during this transitional period are not uncommon.

Serial Attached SCSI (SAS) was specifically developed to reject this “two steps forward, one step back” phenomenon. Utilizing the same SCSI commands as its parallel predecessor, SAS employs three different protocols to transport information over its serial interface: Serial SCSI Protocol (SSP), SCSI Management Protocol (SMP) and Serial ATA Tunneling Protocol (STP). SSP communicates with SAS devices and existing SCSI software, SMP manages SAS’s point-to-point topology, and STP enables SAS controllers to identify and communicate with Serial ATA devices. Current SCSI software and middleware merely require minor SMP and STP modifications to function in a SAS environment.

As a result Serial Attached SCSI retains the familiar strengths of parallel SCSI (enterprise-class reliability, mature and robust command set, enormous installed base of SCSI applications), while achieving dramatic advances in performance, scalability and compatibility:

Three Steps Forward…

  • Performance: With an astounding transfer rate of 3.0 Gb/s (and a clear roadmap to 12.0 Gb/s), Serial Attached SCSI accelerates enterprise storage to breathtaking speeds by utilizing full-duplex, point-to-point architecture.
  • Scalability: Inexpensive switches known as expanders enable easy aggregation of many drives, allowing a single SCSI domain to contain over 16,000 devices while preserving performance.
  • Compatibility: SAS backplanes and host bus adapters (HBAs) are fully compatible with Serial ATA (SATA) drives, giving unparalleled freedom to choose the optimal solution for a given application.

No Steps Back

  • Serial Attached SCSI leverages current investment in storage management and enterprise application software by integrating the same SCSI command sets that support today’s enterprise storage environment. Migration to SAS is straightforward, with no need for the system-level workarounds required by ATA.

As constrained budgets put growing pressure on IT departments to justify expenditures, storage solutions that leverage the value of existing infrastructure are increasingly compelling. By preserving investment in SCSI applications while adding revolutionary performance and flexibility, Serial Attached SCSI sets a new standard for efficient enterprise storage solutions.

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