TORONTO – As more NVM Express (NVMe)-capable SSDS debut and the protocol gains traction, more controllers are hitting the market to allow storage infrastructures to get the most from these drives. In the meantime, PCI Express (PCIe) is seeing more adoption in storage applications
PMC-Sierra announced two new offerings leveraging both technologies, using this week’s Flash Memory Summit as the launch pad: its second-generation Flashtec NVMe controllers and Switchtec PSX PCIe storage switches.
The latest Flashtec NVMe2032 and NVMe2016 controllers integrate DDR4 DRAM to get the most throughput and reduce bottlenecks. In a telephone interview with EE Times leading up to the Flash Summit, David Allen, director of product marketing for PMC-Sierra’s performance storage products, said the Flashtec controllers can handle a wide variety of NAND for the next 10 years, including 3D, TLC, MLC and SLC with Toggle or ONFI interfaces, as well as TSV implementations.
Allen said SATA has been prevalent for “low cost, reasonable performance applications," but Flashtec controllers are focused on consistent low latency for enterprise and hyperscale environments, including NV-DRAM applications. He said the NVMe ecosystem has grown to provide a great deal of flexibility for customers and a broad range of drivers for Windows, Linux and Solaris.
Historically, said Allen, PCIe was not built for storage, but the combination of Switchtec storage switches and Flashtec controllers will allow enterprises to more reliably scale SSD performance using PCIe within data center environments. The Flashtec controller can support more than 20TB of flash capacity – 16TB flash capacity using 256Gb flash density; however, IOPS would suffer at that top end, he said. Meanwhile, a Switchtec switch can reliably pool a large number of PCIe drives.
PMC-Sierra said its single chip Switchtec storage switch can support a 40 SSD array
In an email interview with EE Times, Loring Wirbel, senior analyst at The Linley Group, said PMC’s Switchtec was the first PCIe switch optimized for storage networks that he had seen, noting that Mellanox is merging Infiniband and Ethernet switching in products which could offer PCIe interfaces. He said the benefits of Switchtec and Flashtec being based on PCIe is that it is a very flexible standard, and in some ways, even more so than Ethernet switches. “Ethernet is the broadest standard, but not really ideal as a system switch."
At the Flash Summit, Mellanox and PMC-Sierra announced a combination of Mellanox PeerDirect RDMA and PMC Flashtec NVRAM Drives that enable peer-to-peer transactions directly between PCIe devices, freeing up the CPU and DDR bus. They also demonstrated NVMe over RDMA using the Flashtec NVRAM Drive’s NVMe interface and Mellanox’s ConnectX-3 Pro network card.
Until recently, PCIe hasn't been used much outside of realms in the backplane or server cage, or rack to rack, Wirbel said. “I've always believed PCIe could achieve greater things in topologies almost as big as LANs." The benefits of PMC's specific Switchtec device, he said, is that it integrates SERDES physical-layer interfaces and a high-end MIPS multicore processor. “The latter can offer some pretty advanced programmable features such as multi-host and virtual switch partitions. Some storage networks will get to be pretty complex and hierarchical in the future."
Flashtec supports multiple flash types, including 3D NAND
Wirbel said few controllers are PCIe-based, and not many have adopted the NVMe protocol, which could be a blessing or a curse. “NVMe seems very useful, but is not yet a true standard," he said. “It’s too early to tell if the protocol will win the space."
While NVMe is relatively new and not entirely proven to be the standard going forward, it’s gaining ground as vendors ship new SSDs using the specification for both servers and workstations. The NVM Express Work Group decided to incorporate itself last year to further the NVMe specification.
Established as a working group under the guidance of Intel, it released the first NVM Express specification in March 2011. It outlines a standardized register interface, command, and feature set for PCIe-based storage technologies such as SSDs, designed specifically for nonvolatile memory.
Wirbel said that in most cases, Flashtec won't be competing against other NVMe controllers, but other SATA controllers. “SATA is simply an aging protocol."
PMC-Sierra has always been a leader in SAS and SATA, he added, and by offering two programmable devices based on PCIe, it is entering a new market with a smart strategy; Wirbel believes PCIe will be the dominant architecture everywhere.
Although alternatives to PCIe have emerged, it still has its advantages, particularly its scalability, and there is a roadmap for PCIe for the next several years. Products with gen 3.x will be available roughly from now until 2017, with gen 4 expected by 2018.
—Gary Hilson covers memory and flash technologies for EE Times and is the editor of Memory Designline.