SAS: Isn’t Going Anywhere Anytime Soon

Article By : Gary Hilson

There’s a trend toward replacing SATA SSDs, which have become a ubiquitous choice for IT managers and data center architects due to their low cost and compatibility, with SAS infrastructures.

Replacing SAS may be driving some NVMe adoption, but SAS isn’t going anywhere anytime soon — customers still expect innovation from the serial attached SCSI interconnect.

Kioxia America, Inc., once known as Toshiba Memory America, recently completed 24G SAS End-to-End Storage interoperability testing in collaboration with Microchip Technology. The interoperability testing shows how Kioxia’s 24G SAS SSDs and Microchip’s suite of 24G SAS products can be combined in new server and storage systems to increase performance while maintaining backward compatibility with existing infrastructure. Included in the tested products were Microchip’s SmartROC 3200 PCIe Gen 4 Tri-Mode RAID-On-Chip (ROC) Controller, the SmartIOC 2200 Input/Output Controller (IOC), and the SXP 24G SAS expander.

Steve Garceau, director of marketing for enterprise SSDs at Kioxia, said the doubling of bandwidth to 24G is appealing for server systems that can take advantage of the bandwidth. Customers also want flexibility as to what media types they use so they can easily repurpose servers down the road if need be. He said there’s a trend toward replacing SATA SSDs, which have become a ubiquitous choice for IT managers and data center architects due to their low cost and compatibility, with SAS infrastructures, Flash-based SSDs tend to be bottlenecked by SATA’s 6Gb/s performance ceiling.

When you also consider there’s no substantive improvements in the near-future roadmap for SATA, said Garceau, there’s a demand for something proven and familiar that can handle I/O-intensive workloads by giving applications access to higher performing and lower latency storage. Kioxia’s offerings include its PM6 Series that use its BiCS 3D flash memory technology with capacity as high as 30.72 TB and all the enterprise-class features customers have to expect, he said. For example, the SAS interface uses SCSI commands geared toward error recovery, error reporting, and block reclamation to meet reliability expectations. “It’s all the bells and whistles, all the performance, and all the endurance,” he said.

Even with increasing interest in NVMe, the SAS interface still has clear roadmap, evolving from 3 Gb/s to 24G with 48G upcoming. (Source: Kioxia)

The company is also offering a value SAS SSD, a new class that it expects will replace enterprise SATA SSDs in most server applications as they become a bottleneck to the server, preventing the CPU from reaching its operational or transactional potential for many applications. Garceau said the continued demand for SAS by OEMs boils down to flexibility and manageability. “It’s a stable interface, and 24G provides that doubling of bandwidth over the previous generation. That’s really big for those OEMs that want to maximize the performance while maintaining hybrid system and flexibility — that ability to stuff SSDs and HDDs into the same system.”

Jay Bennett, senior of manager of product marketing for Microchip’s data center and solutions business unit, said SAS is far from being eclipsed by NVMe, which is well suited for high-performance requirements of high-end SSD technology. “SAS is meant to service a very broad set of cost and performance points that are outside of the high end of the performance range.” There’s also a level of familiarity that customers are comfortable with, he said. “SAS has a well-established ecosystem of software and hardware, and it’s a well-understood technology for server and storage OEMs.”

And while there’s a lot of excitement around NVMe, said Bennett, it does require a high level of investment, and there’s still room for innovation around SAS. Microchip’s high-performance interoperability testing at 24G with Kioxia is example of the opportunities for SAS. The SAS-4/SPL-5 standard complements the latest PCIe Gen 4 data center input/output (I/O) specifications, he said, while doubling the storage interconnect bandwidth of its predecessors.

Kioxia’s latest SAS SSD offerings include its PM6 Series with capacity as high as 30.72 TB and a wide range of enterprise class features, as well as its Value SAS (vSAS) SSD, designed to replace enterprise SATA SSDs in most server applications. (Source: Kioxia)

Jeremiah Tussey, Microchip’s alliances manager, said current SAS capabilities balance delivering high performance for the workloads that need more than what they’re able to get from SATA, allowing for more efficient use of both new and legacy storage infrastructure. A lot of Microchip’s focus is on the mainstay technologies rather than the new and fancy technologies because there’s a need to maintain and leverage the existing ecosystem and infrastructure while optimizing towards what’s needed for the next generation, he said. For 24G SAS, it includes focusing on maintaining the data rate and the signal integrity, which is critical. “It’s not a particular focus area for NVMe per se, but it is a strength for SAS.”

Microchip is also focused on advancements on the hard drive side along with SSDs, including shingled magnetic recording (SMR) that efficiently increases areal density and capacity. Overall, said Tussey, Microchip is looking to enable an ecosystem over the long term for customers that have invested in both SATA and SAS because they don’t want to see it go away.

Bennett said Microchip’s controller products are built to enable its end customers to support all different types of media seamlessly. “SAS is far from dead, but also people want to be able to access that the latest and greatest in NVMe and that’s part of our product offering as well.”

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