Commodity Memory for a High Performance World: The View from Samsung
As CPUs get ever more powerful, their hunger for data is outstripping the ability of memory systems to feed them. This is especially true in high performance computing, where memory capacity is often constrained by cost, and more recently, energy consumption. With larger supercomputers now incorporating upwards of hundreds of terabytes of main memory, and often with multiple terabytes of flash storage, this challenge will continue to grow.
As one of the world leaders in memory solutions, Samsung Semiconductor has been a key supplier of DRAM and NAND components that end up in high performance computing systems. Dr. Byungse So, who heads the Memory Product Planning & Application Engineering team at Samsung, shares his thoughts about the memory technologies needed by performance-minded users today and what might come next.
HPCwire: The memory wall is perhaps one of the biggest impediments in high performance computing today. What is the main reason that DRAM performance has failed to keep pace with processor performance?
Byungse So: In current system architectures, the CPU always needs high bandwidth and high density memory with low cost to keep feeding data to the computing engine. Therefore system memory has typically been a module-based commodity solution using multiple standard DRAM components. Due to its cost-driven design, system performance is compromised. It is time to shift gears by switching from cost-optimized to performance-optimized designs via application specific memory.
HPCwire: So what types of innovations will be needed? Are there DRAM technologies on the horizon that promise to do this?
So: Samsung has been exploring ways of narrowing the gap. Short term, Samsung will continue to provide the highest speed system and graphic memory. In the long run, Samsung will be investigating new interface technologies to meet high bandwidth requirements aimed at double-digit performance improvements over DDR3. To make this happen, close collaboration with CPU producers, platform builders as well as system users, is required.
HPCwire: Memory capacity can be an additional impediment to performance. Given the need for terabytes of memory for some HPC applications and the expense that entails, is there a way to build reasonably-priced systems that can support big memory applications?
So: Samsung has been leading the market with the highest capacity memory solutions and is already providing solutions which allow building terascale system memory for a single dual-processor system. Combined with the most advanced production process, Samsung will keep investigating how new stacking technologies including 3DS — 3D-Stacking –can allow adequate memory support of even most capacity-hungry systems.
HPCwire: The commodity DRAM business is well known for being rather unforgiving to suppliers, with some firms like OCZ exiting the market and others like Qimonda eventually going bankrupt. Why is the DRAM business so precarious and how has Samsung managed to maintain its viability in this segment?
So: DRAM as commodity memory has been under continuous pressure from its primary users, that is, the PC and notebook market, to continuously lower its cost. This enormous cost pressure has kept a number of suppliers in the red for a long time, ultimately pushing some suppliers out of the market, while also leading to designs compromising between cost and performance. Samsung’s way out of this dilemma is a combined focus on industry-best economies of scale, industry leading process technology and optimized, application-oriented product solutions for both mobile and server applications.
HPCwire: How do you think NAND memory technology can best be applied in high performance computing systems?
So: Solid state drives are the next-generation storage devices that have overcome the shortcomings of rotating media in high performance computing systems. The SSD adoption rate in volume servers is supposed to grow dramatically. Its interface will slowly be changing from SATA to SAS or PCIe for easy migration.
The most important parts in this emerging product line are the NAND flash components as well as the controllers which manage the input and output of data. Other major components are DRAM, which help buffer during data input and output, and the firmware that drives an SSD.
Samsung is able to combine its extensive know-how, stemming from the design and the production of billions of NAND flash and DRAM components, with its long history of designing countless controllers and firmware, as a company not being “only” vertically integrated.
HPCwire: Are there other solid state memory technologies that you believe will prove their worth commercially? If so, how will they change the memory-storage hierarchy?
So: Many studies and researches on fast non-volatile memory have been conducted in the past years, such as PRAM and MRAM as potential future memory technologies. However, more time is needed to examine their commercial value, as currently no existing hardware can fully utilize the features of these NVM solutions in their different roles.
Based on the maturity of the chosen technology, the usage model might also affect the memory hierarchy. It seems quite obvious that DRAM speed like fast NVM can change the existing memory hierarchy. OS experts may have better answers to this question.
HPCwire: Will these newer technologies eventually displace NAND or even DRAM?
So: It will take more than just better technology to replace existing memories, as they possibly impact system architecture and the value chain. Hence we expect that these new technologies will slowly penetrate into different parts of systems and industries and start to gradually build a new ecosystem. Eventually though, a large portion of NAND and DRAM will be replaced.
Dr. So will be delivering a keynote on advanced memory technology at this year’s International Supercomputing Conference (ISC’12) in Hamburg Germany. His presentation will take place on Tuesday, June 19.