6Gb/s Serial-Attached SCSI (SAS)

6Gb/s Serial-Attached SCSI (SAS)
Whitepaper | March 2009
6Gb/s Serial-Attached SCSI (SAS)
The foundation of an enterprise computing environment is based on high performance and high reliability.
HGST understands that multi-user enterprise systems require the fastest technology available to meet their
data-intensive processing needs. To address these requirements, HGST is working with industry leaders to
double current storage performance standards with the introduction of 6Gb/s Serial-Attached SCSI (SAS)
solutions. Fully interoperable with existing SAS 3Gb/s technology, the new
SAS solutions will double data storage I/O rates to 6Gb/s. New SAS 6Gb/s hard
drives from HGST provide a key component of the overall SAS infrastructure,
and will help meet the ever-increasing performance requirements of enterprise
Initially introduced in 2004 at 3Gb/s, SAS interfaces significantly increased the
available bandwidth offered by SCSI-based storage systems. The current introduction of SAS 6Gb/s doubles the available bandwidth of high-performance
storage systems. HGST is already working with industry leaders to develop the next-generation SAS infrastructure, which will double throughput again to 12Gb/s in the 2012 timeframe. As with previous performance upgrades, the future 12Gb/s SAS components will be fully interoperable with existing SAS solutions.
SAS 6Gb/s—Enterprise-class Storage Solutions from HGST
The market for storage solutions is currently evolving toward two technologies: Serial ATA (SATA) for singleuser systems where performance is less critical, and SAS for enterprise applications where performance and
reliability are primary requirements. Legacy technologies, such as SCSI and parallel ATA (PATA), are being
replaced by SATA and SAS. Fibre Channel will continue to serve as a system interconnect structure, but its
use as a storage device interface is expected to diminish and eventually be replaced by SAS. HGST has also
announced plans to deliver flash-based solid-state drives (SSDs) with SAS and Fibre Channel interfaces early
in 2010.
Fast response time is critical for a wide range of enterprise applications, including online transaction
processing, real-time business analytics and timely delivery of data-intensive content-on-demand, such as
multiple channels of streaming video. 6Gb/s SAS-based solutions are ideal for meeting these challenges and
are also well-suited for environments supporting scientific workstations or other infrastructures with complex paths and high volumes of I/O traffic. Fast throughput, reliability and scalability are essential in these
applications. SAS 6Gb/s solutions from HGST will deliver the following key benefits:
• Double storage system bandwidth from 3Gb/s to 6Gb/s
• Preserve hardware investments by enabling two SAS 3Gb/s devices to be multiplexed to deliver
6Gb/s throughput
• Enhance configuration flexibility by enabling a single storage solution to be associated with, and discovered by, multiple hosts via expander zoning
• Provide dual interfaces that enable a SAS array to be connected to two different systems or support faulttolerant redundant connections to the same system
• Increase cabling lengths from 6 to 10 meters and support mini-SAS connectors for more space-efficient
wiring installations
• Provide support for SATA-based storage arrays
6Gb/s Serial-Attached SCSI (SAS)
Whitepaper | March 2009
Preserves Hardware Investments
As an evolutionary technology, SAS 6Gb/s extends the viability of your existing investments in SAS 3Gb/s
systems. A fully interoperable solution, IT personnel have the choice of leaving SAS 3Gb/s systems in place or
multiplexing them together to achieve higher bandwidth through migration to SAS 6Gb/s technology.
Enhances Configuration Flexibility
SAS 6Gb/s delivers several enhancements that deliver additional flexibility when configuring enterprise
data center infrastructures. Extending cabling distances from six to 10 meters provides a wider range of
configuration options in data centers that have grown increasingly complex. Support for 6Gb/s mini-SAS
connectors provides more space-efficient, cleaner cabling options between systems and large disk arrays.
SAS 6Gb/s drives from HGST are configured with dual ports so that two different systems can access the
same drive or redundant connections can be established for additional system resiliency.
As shown in Figure 1, the high-performance SAS 6Gb/s infrastructure provides enterprise servers with fast
access to a variety of data storage systems. This configuration was successfully demonstrated at the SCSI
Trade Association Open House held in San Jose, CA in May, 2008. A host bus adapter (HBA) is used to provide
connectivity between the server and a SAS 6Gb/s expander. The role of the SAS expander is to provide additional ports for attachment of peripheral units, such as the SAS 6Gb/s hard drives depicted in blue.
Directly below the SAS 6Gb/s expander is a SAS 6Gb/s analyzer, which is deployed to monitor network traffic between the two SAS 6Gb/s expanders. The lower SAS 6Gb/s expander functions as a connection path to
multiple lower-performance storage systems, including three SAS 3Gb/s hard drives and three SATA 3Gb/s
hard drives.
SAS 6Gb/s
SAS 6Gb/s
SAS 6Gb/s
SAS 3Gb/s HDDs
SAS 6Gb/s HDDs
Figure 1. The SAS 6Gb/s infrastructure is ideal for providing servers with high-speed connectivity to data storage
systems across the enterprise computing environment
6Gb/s Serial-Attached SCSI (SAS)
6Gb/s Serial-Attached SCSI (SAS)
Whitepaper | March 2009
Each host bus adapter port provides 6Gb/s of bandwidth to its attached devices. Devices across the SAS
infrastructure are provisioned with full 6Gb/s connectivity, and are able to transfer data at their maximum
speed dependent on current port topology loading conditions.
• Two 6Gb/s devices on the same HBA port transferring data at different times will benefit from full 6Gb/s
• Two 6Gb/s devices on the same HBA port transferring data simultaneously will share 6Gb/s of bandwidth
• Two 3Gb/s devices on the same HBA port transferring data simultaneously can be multiplexed so that
both devices operate at full bandwidth over the 6Gb/s connection
Increased Performance for Enterprise Computing Environments
SAS 6Gb/s will bring a wide range of benefits to ever-expanding enterprise data centers, and the new
generation of SAS 6Gb/s drives from HGST will be at the heart of the new installations. By combining high
performance with industry-leading reliability and innovative design, HGST continues to lead the way as
enterprise computing evolves to meet the demands of the future.
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Product specifications provided are sample specifications and do not constitute a warranty. Information is true as
of the date of publication and is subject to change. Actual specifications for unique part numbers may vary. Please
visit the Support section of our website, www.hgst.com/support, for additional information on product specifications.
Photographs may show design models.
One GB is equal to one billion bytes when referring to hard drive capacity. Accessible capacity will vary depending
on the operating environment and formatting.
© 2012 HGST, a Western Digital company
HGST, a Western Digital company
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San Jose, CA 95135 USA
Produced in the United States 3/09.
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6Gb/s Serial-Attached SCSI (SAS)
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