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Faster Than Flash; Micron Releases NVDIMM Products

By - Source: Micron

The emergence of SSDs served as the catalyst for an entire rethinking of how we tackle performance workloads by enabling explosive new levels of performance -- but even in the midst of the SSD explosion, the datacenter never stands still.

Micron released its new family of DDR4 NVDIMM (Non-Volatile Dual Inline Memory Module) products to help address the needs of the most demanding workloads. The inaugural products come in 8 GB capacities, and a 16 GB product will be available in early 2016. Larger capacities with even more DRAM capacity are on the horizon, and Micron indicated its intention to use this same platform with its forthcoming 3D XPoint technology.

All-flash arrays provide incredible performance and would seem to be the go-to answer for bleeding edge applications, but even the efficient and powerful RoCE (RDMA Over Converged Ethernet) and NVMe Over Fabrics techniques cannot entirely negate network latency. Server-side flash deployments, in all of their various forms, provide the best performance by placing the data as close to the CPU as possible. However, the push is already on for the next level of performance, and in-memory storage architectures are becoming a popular solution for performance-hungry applications.

In-memory storage leverages DRAM for data storage, similar to a typical RAM drive. DRAM is exponentially faster than flash and offers unlimited endurance, but it lacks persistence. Persistence is a pesky requirement that complicates data storage, and it merely indicates that the data should still be present if power is removed from the device -- ideally, we want data chiseled in stone the very millisecond it is written.

Unfortunately, DRAM is a volatile storage medium that loses all data the moment power is removed, which is not ideal during an unplanned power loss event. A new breed of storage-class memory products are emerging that circumvent the power problem by providing DRAM with the same characteristics as other types of persistent storage.

It is important to note that Micron's NVDIMM products are in a different class (NVDIMM-N) than SanDisk's ULLtraDIMM (NVDIMM-F), which merely places flash on the memory bus. The Micron NVDIMM utilizes a layer of DRAM as storage, but in the event of an unexpected power loss event, the device saves the data in the DRAM to the embedded NAND flash using the power stored in a tethered supercapacitor. This ensures all data written to the device is safe and allows users to realize the speeds of DRAM for storage applications.

Some operations, such as metadata, are extremely taxing on even the fastest SSDs. The ability to write to DRAM as a persistent volume opens up a host of capabilities and allows its use as a cache for flash storage, which increases speed and boosts endurance. This is a popular choice for all-flash arrays, and NVDIMMs are also applicable in big data analytics, RAID caches, In-Memory Databases and OLTP applications.

The NVDIMM market was valued at $1.35 million in 2013, but it will balloon to $570 million by 2020 according to Transparency Market Research. Micron is tapping a fast-growing segment, but there are numerous established players on the field, including Viking Technology and AgigA Tech. Micron is actually co-developing its NVDIMM products with AgigA Tech and utilizing its PowerGem capacitors in its designs. AgigA Tech designed its PowerGem capacitors for deployment into high-heat environments for extended periods of time, and Micron provides monitoring functionality for the supercapacitor.

Micron also provides the option to route a dedicated 12V UPS power supply to the module, which is a significant differentiator in comparison to other products on the market. In-chassis UPS batteries (such as some used in recent OCP designs) are becoming popular, and the ability to leverage the existing hardware instead of adding another component is always a desirable attribute.

Micron's product is similar to other competing entrants and offers both block-addressable and bit-addressable modes, which allows the NVDIMM to appear to the host either as a standard storage volume or as a memory mapped device (DMI).

What separates Micron from the competition (in addition to the forthcoming 3D XPoint models) is that it actually fabricates its own components. Producing its own DRAM allows Micron to inject some of the features typically found as separate components, such as the high speed switches, directly into the DRAM itself. This provides MUX functionality with no additional cost. This more efficient approach reduces cost and potential failure points, and Micron is infusing the features into a number of its other DDR4 products in the future.

Micron also utilizes a pseudo-SLC layer in the NAND to increase the speed of data backup operations from the DRAM to the NAND (within 60 to 90 seconds). Micron will enjoy a significant cost advantage over third-party NVDIMM manufacturers, which may place significant price pressure on its competitors.

Micron is employing both a legacy command set, which is already qualified, and is working on qualifying the JEDEC spec. The company indicated that it feels the JEDEC spec is the way forward, which is an encouraging development for the future 3D XPoint models. All future Micron NVDIMM solutions will leverage the JEDEC firmware interface, which the JC-45 Committee for Memory Modules developed.

Micron is not releasing performance specifications as of yet, but this class of device typically offers several million IOPS and incredible bandwidth directly from the DRAM layer. Micron's NVDIMMs are already shipping in quantity, and three models are available.

  • 8 GB DDR4 NVDIMM with legacy firmware
  • 8 GB DDR4 NVDIMM with JEDEC firmware
  • PowerGEM ultracapacitor for 8 GB NVDIMM

Paul Alcorn is a Contributing Editor for Tom's IT Pro, covering Storage. Follow him on Twitter and Google+.

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