The rapid adoption of flash storage is boosting NVM Express (NVMe), but it’s premature to write obituaries for SAS and SATA.
TORONTO – A recent report forecasting pending dominance of NVM Express (NVMe) as an interface in all flash storage arrays doesn’t mean it’s time to write the obituaries for SAS (serial attached SCSI) and SATA (serial advanced technology attachment) drive interconnects.
NVMe’s rise and expansion as a standard over the past decade, including NVMe Over Fabric, is due in large part to its ability to fully unleash the performance of NAND flash in SSDs. According to the Data Center Storage Equipment Market Tracker from IHS Markit for the second quarter of 2019, the overall all-flash array storage segment decreased quarter over quarter, but all-flash NVMe-drive based versions rose. The research firm reported that revenue rose during the quarter for performance-optimized arrays, a new category based on flash NVMe drives, while revenue fell for all flash performance arrays, which is the larger category based on SAS drives.
So, what’s the long-term outline for SAS? And SATA?
In a telephone interview with EE Times, IHS principal analyst Dennis Hahn said the adoption of NVMe SSDs in all-flash arrays is ramping up because the interface standard has proven itself in servers quickly for all flash storage systems. “SAS was really designed around spinning disks,” he said.
It’s those spinning disks, however, that in part are why SAS continues as an interface for SSDs in servers, he said, because many customers still want to mix and match. “People want to intermix drives in the same system without having different pieces of hardware behind them. There are also a lot of people that are still concerned about the robustness of NVMe.”
While that robustness will happen over time, Hahn said SAS still meets the performance needs of many users as a drive interconnect at the back end. Long term, NVMe’s appeal is its end-to-end ability to supplant SAS and SATA at the backend and front-end storage system interconnects such as iSCSI and Fiber Channel with NVMe Over Fabric and NVMe over TCP. He said the latter will kill off iSCSI rather quickly. Similarly, most people assume SATA will go away over time. “It’s got cost advantage right now just because it has the volume. But over time that seems to be going away quickly as well. It’s got a real performance disadvantage. It’s even below SAS as a performance interconnect for drives.”
The death of SATA has been predicted for some time, but Micron Technology has opted to continue to support the interconnect while eschewing SAS. It recently launched its 5300 3D TLC NAND enterprise SATA drive, designed for read-intensive, mixed uses in data center and cloud environments. “We’re seeing a lot of strength in SATA right now, and it’s a business that’s certainly not declining yet,” Matt Shaine, Micron’s senior product line manager of SSDs. Although Micron sees the future as NVMe in terms of overall market bit growth, SATA still meets the needs of many workloads and budgets.
Ease of integration and familiarity are just as important to customers, he said, with millions of deployed SATA sockets in the world. “We obviously don’t see as many customer qual problems or qual issues with SATA as we’ve heard anecdotally on the NVMe side.”
Shaine said NVMe is akin to the shiny new Ferrari on the road. While some customers are migrating their platforms to it, SATA remains a trusted alternative for wide range of workloads that vary depending on the customer’s specific needs because the specification offers good enough performance. Even when a large portion of storage needs are moved to NVMe, the boot portion remains on SATA. “It’s a mixed bag.”
Shaine said enterprise customers tend to be somewhat conservative and go with what they know. Any new technology needs to be proven out before they make the leap. “But, again, there’s a portion of the market that that just doesn’t necessarily need the extra performance.” Industrial customers are one such segment, he said.
Typically, SATA customers are ripping and replacing, said Shaine, and for the most part, Micron doesn’t get many new feature requests. “If it’s a server refresh, customers expect the new drives to be at least as good or as close to what they’re pulling out as possible.” However, the company is seeing more interest around security of drives. In the case of the recently launched 5300, TCG Opal support was added based on market demand from customers.
In the meantime, average capacity for SATA drives is relatively flat over time, said Shaine, and the majority Micron customers want to continue see a long-term roadmap for the interface standard. “We don’t see it disappearing for the foreseeable future. We see it as a market that’s going to be steady and stable for the next several years.”
While Micron focuses on servicing SATA customers and moving forward with NVMe, Western Digital continues to see a lot of market demand for SAS. The
company’s sixth generation Ultrastar SAS SSD comes on the heels of two busy quarters announcing two data center-class 96L NVMe SSDs and its NVMe over Fabrics platform with OpenFlex. Eric Pike, director of Western Digital’s enterprise devices group, said enterprise storage customers globally are still turning to SAS to accelerate their mission-critical workloads and support ever-increasing data volumes. The Ultrastar DC SS540 SAS SSD comes in multiple endurance SKUs aimed at Tier-0 enterprise storage, high-performance computing (HPC) and software-defined storage (SDS) environments.
“Everybody’s working on NVMe. They’ve been working on NVMe for many years now,” he said. “But as we all know in the enterprise world, transitions happen over a fairly long period of time.” On a petabyle basis, there remains a very healthy SAS market, just as there continues to be a healthy one for SATA.
Even though NVMe is growing faster, Pike said enterprise markets for SAS are stable in part because it is in fact good enough for customers. But they’re also wary of putting mission critical data at risk as they try to transition to a new interface — these are things that keep people who manage large-scale data centers and large-scale IT infrastructure awake at night. “SAS has been a very stable and very powerful solution for customers for some time now,” he said. “They want to keep that stability.”
And as much as many organizations want to be ready for NVMe, including NVMe Over Fabric, Pike said there are some workloads that just don’t need the performance or feature sets the standard offers. For example, SAS is still used in server attached environments, where NVME today is still struggling with infrastructure build out. “Our customers are introducing NVMe systems and it is a key priority for them to have these new NVMe systems out there,” he said. “We absolutely believe in the future of NVMe, but in order to service that large portion of the business in SAS, you have to keep introducing new products with new technology and scalability without cost to keep those other customers who aren’t going to be on the front edge of the curb.”
IHS’ Hahn said the lag for servers in NVMe adoption is the result of users being risk adverse and their comfort level with SAS, but emerging workloads such as machine learning and artificial intelligence are driving the market of NVme and data processing performance. “Now the storage systems guys want to get into that whole game. They don’t want to be left out of that whole segment that’s emerging so quickly.”