Netlist and the Present
Netlist are the owners of the patent on key parts of Sandisk’s UtraDIMM technology (licensed from Diablo Technologies originally, I believe). While Netlist has lawsuits going back and forth regarding its intellectual property, it continued to develop products. Here now is the EXPRESSvaultTM EV3 announcement. It’s a PCI RAM disk of sorts that backs up the RAM with a ultracapacitor/battery combo. If power is lost an automated process backs up the RAM to onboard flash memory for safe keeping until power is restored. This design is intended to get around the disadvantages of using Flash memory as a disk and the wear and tear that occurs to flash when it is written to frequently. Less expensive flash memory suffers more degradation the more you write to it, eventually memory cells will fail altogether. By using the backing flash memory as failsafe, you will write to that flash only in the event of an emergency, thereby keeping the flash out of the grindstone of high levels of I/O. Note this is a very specific niche application of this technology but is very much the market for which Netlist has produced products in the past. This is their target market.
The Future is lower latencies-Enter UltraDIMM
Turn now to a recent announcement by Lenovo and it’s X6 server line announcing further adoption of the UltraDIMM technology. Lenovo at least is carrying on trying to sell this technology of Flash based memory interspersed with DRAMs. The idea of having “tiers” of storage with SSDs, UltraDIMMs and DRAM all acting in concert is the high speed future for the data center architect. Lucky for the people purchasing these things Netlist and Diablo’s legal wrangling began to sort itself out this Spring 2015: http://www.storagereview.com/diablo_technologies_gains_ground_against_netlist_in_ulltradimm_lawsuit
With a final decision being made fairly recently: http://www.diablo-technologies.com/federal-court-completely-dissolves-injunction/
Now Diablo and Sandisk and UltraDIMM can compete in the marketplace once more. And provide a competitive advantage to the people willing to spend the money for the UltraDIMM product. By itself UltraDIMM does make for some very interesting future uses. More broadly the adoption of an UltraDIMM like technology in laptops, desktops, tablets could see speed improvements across the board. Whether that happens or not is based more on the economics of BIOS and motherboard manufacturers than the merit of the design engineering of UltraDIMMs. More specifically Lenovo and IBM before that had to do a lot of work on the X6 servers to support the new memory technology. Which points to another article from the person I trust to collect all the news and information on storage worldwide, The Register’s Chris Mellor. I’ve followed his writing since about 2005 and really enjoyed his take on the burgeoning SSD market as new products were announced with faster I/O every month in the heady days of 2007 and beyond. Things have slowed down a bit now and PCIe SSDs are still the reference standard by which I/O benchmarks are measured. Fusion-io is now owned by Sandisk and everyone’s still enjoying the speed increases they get when buying these high end PCIe products. But it’s important to note for further increases to occur, just like with Sandisk’s use of UltraDIMM you have to keep pushing the boundaries. And that’s where Chris’s most recent article comes in.
Memory Meshes, Present and Future
Chris discusses the how Non-Volatile Memory Host Controller Interface (NVMHCI) came about as a result of legacy carry-over from spinning hard drives in the AHCI (Advanced Host Controller Interface) standard developed by Intel. AHCI and SATA (Serial ATA, the follow-on to ATA) both assumed spinning magnetic hard drives (and the speeds at which they push I/O) would be the technology used by a CPU to interact with it’s largest data store, the hard drive. Once that data store became flash memory, a new standard to drive faster access I/O and lower latencies needed to be invented. Enter the NVMe (Non-volatile Memory Express) interface, now being marketed and sold by some manufacturers. A native data channel from the PCI bus to your SSD however it may be designed, is the next big thing in hardware for SSDs. With the promise of better speeds it is worth migrating, once the manufacturers get onboard. But Chris’s article goes further to really look out beyond the immediate concerns of migrating from SATA to NVMe as even Flash memory may eventually be usurped by a different as yet unheard of technology. Given that’s the case, NVMe abstracts enough of the “media” of the non-volatile memory that it should allow future adoption of a number of possible technologies that could usurp the crown of NAND memory chips. And that potentially is a greater benefit than simply just squeezing out a few more Megabytes per second read and write speed. Even more tantalizing in Chris’s view is the mixing of DRAM and Flash memories in a “mesh” lets say of higher and lower speed memories like Fusion-io’s software uses to make the sharp distinction between DRAM and Flash less visible. In a sense, the speed would just come with the purchase of the technology, how it actually works would be the proverbial magic to the sysadmins and residents of Userland.
The ever-increasing density of virtual infrastructures, and the need to scale databases larger than ever, is creating an ongoing need for faster storage. And while flash has become the “go to” performance option, there are environments that still need more. Nonvolatile DRAM is the heir apparent, but it often requires customized motherboards to implement, for which widespread availability could be years away. Netlist, pioneer of NVRAM, has introduced a product that is viable for most data centers right now: the EXPRESSvaultTM EV3.
The Flash Problem
While flash has solved many performance problems, it also creates a few. First there is a legitimate concern over flash wear, especially if the environment is write-heavy. There is also a concern about performance. While flash is fast compared to hard disk drives it’s slow when compared to RAM, especially, again, on writes.
But flash does have two compelling advantages over DRAM. First it is…
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