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24G SAS Technology

The New Storage Backbone of the Data Center

The demands of data storage and performance have increased tremendously since SCSI was developed 30 years ago. Replacing SCSI more than a decade ago, Serial Attached SCSI (SAS) is now the primary point-to-point serial protocol that is used to move data to and from computer storage devices such as Solid State Drives (SSDs), Hard Disk Drives (HDDs) and tape drives. We have watched SAS transition over this time as performance demands continue to increase, doubling the performance of each new generation from the original 3 Gbps to 6 Gbps to 12 Gbps, on to the current mainstream generation of 24 Gbps. 

24G SAS Technology Generation Roadmap

The Need for a New, Faster Storage Standard

The bandwidth offered by the mainstream 12G SAS, defined at the physical layer by SAS-3, is well matched to the PCIe® Gen 3 storage ecosystem. However, the increase in computational workloads and storage traffic is driving the industry to faster CPU and storage interconnect via PCIe Gen 4.0 and Gen 5.0. The 24G SAS standard, defined at the physical layer by SAS-4, was created to meet the performance needs of the PCIe Gen 4 ecosystem. It supports data rates of 22.5 Gbps to double the data throughput of the previous-generation SAS-3 standard, eliminating storage bottlenecks to SSDs and HDDs in the data center.

24G SAS Technology Standard

What Is Different About the 24G SAS Specification?

24G SAS technology is more than a speed upgrade for the SAS interface. This standard implements a major overhaul of the interface, including the use of 128b/150b encoding, with 20-bit forward error correction, as well as a number of other features and enhancements. The SPL packet encoding scheme also introduces the opportunity for new bandwidth aggregation techniques. The existing SAS value proposition of reliability, availability, scalability, flexibility and low total cost of ownership is preserved. In addition, SAS-4 technology retains backwards compatibility with previous-generation SAS implementations, which means that older drives will be compatible with newer storage controller and SAS expander products.

24G SAS  Features:

  • Doubles the effective storage bandwidth from 1.2 Gbps per lane to 2.4 Gbps per lane
  • Backwards compatibility with SAS-3 (12 Gbps), SAS-2 (6 Gbps) and SATA (6 Gbps)
  • Preserves the existing SAS value proposition of reliability, availability, scalability, flexibility and low cost
  • Protects your storage investment

Dynamic Channel Multiplexing (DCM)

24G SAS with our Dynamic Channel Multiplexing (DCM) provides higher performance than SAS/SATA edge buffering with significantly reduced latency when aggregating lower performance SATA and SAS drives (6G and 12G), ultimately enabling better storage utilization in the data center. DCM technology enables storage subsystems to harness the full performance capabilities of PCIe Gen 4-enabled systems. Fully interoperable with existing SAS and SATA infrastructure, DCM can extend the lifecycle of legacy rackmount storage by aggregating throughput within the SAS fabric.

We have collaborated with Teledyne LeCroy to develop test tools for DCM, ensuring that our partners can efficiently deploy this innovative technology. With the introduction of the first 24G SAS analyzer, jammer and exerciser system, Teledyne LeCroy has now assembled the most complete line of protocol layer test tools for storage vendors targeting 24G SAS development.

Who Will Benefit from 24G SAS?

The need for increased storage performance affects organizations across practically every industry, including hyperscale data center, banking, education, government, healthcare and manufacturing. All data centers will continue to require SAS or SATA media—whether that be SSDs or HDDs—for mission-critical data. As the industry transitions to PCIe Gen 4, SAS-4 will become increasingly relevant to ensure that the CPUs are not starved for storage bandwidth to ever increasing terabytes of stored user data.

Visit our Smart Storage Platform page to learn about our selection of 24G SAS RAID-on-Chip (ROC) controllers and Input/Output (IOC) controllers.