The two big trends in flash technology are Non-Volatile Memory Express (NVMe) flash and QLC (quad-level cell) but they are at opposite ends of the spectrum from a use case perspective. NVMe flash is designed for extremely high performance and offers incredibly low latency. QLC flash, on the other hand, is the most cost effective version of flash the market has seen so far. Neither of these flash technologies is perfect for all use cases but when used in combination with each other, storage infrastructures become very interesting.
The NVMe Surge
NVMe flash drives are essentially the same price as SAS/SATA flash drives. The only aspect that makes NVMe a more expensive proposition is the cost of the surrounding storage ecosystem. To get full performance from the drives, storage software has to add additional processing power, additional RAM and sometimes limit available features, which drives up the cost of an NVMe flash array. It is a rare moment in the technological timeline where storage is the fastest component of the architecture. Eventually, storage software will catch up, but even before then it makes sense for most customers to start their NVMe transition now.
The QLC Conundrum
At the other end of the spectrum is QLC, a slower (but still fast when compared to hard disk technology) flash technology with very high densities. The key challenge with QLC is its lack of durability. The typical QLC drive can’t sustain as many writes as TLC (triple-level cell) but as we’ve learned through the progression from SLC (single-level cell) to MLC (multi-level cell) to TLC technologies, there are a lot of variables in calculating how many writes is too many for each technology. However, a detailed discussion is beyond the scope of this briefing note. Several storage system vendors are delivering enterprise class storage systems that leverage QLC technology to drive down the cost of an all-flash solution. In most cases these vendors are using a TLC layer as a buffer to the QLC layer and manage how data is written so as to extend the life of QLC.
Micron’s Role in NVMe and QLC
Micron is a leader in delivering flash solution to the market. Their latest NVMe-based drive, the Micron 9300 SSD series, is designed to deliver the extreme performance one would expect from these drives while also addressing a key flash SSD pain point, write performance. The 9300 series provides equal performance on both reads and writes, claiming the ability to read and write data at 3.5GBs. The 9300 series drives also lowers typical write latency to less than 11 microseconds under typical situations. The combination of technologies combines into a staggering 850,000 read/write IOPS per drive.
Micron’s QLC technology is the QLC based 5210. The 5210 is available in several configurations but is primarily positioned as a hard drive replacement With NVMe TLC flash acting as a buffer the 5210 should see workloads that are not only better suited for it but also where it can provide significant value over hard disk drive workloads. As the workload becomes less random the QLC-based 5210 quickly catches up to the typical hard disk drive in terms of durability, while gaining the performance characteristics typical of flash.
NVMe TLC and SATA QLC – Better Together
The ideal use case is using NVMe TLC in conjunction with QLC. In this configuration the application, operating system or storage software uses the NVMe TLC as a staging area, so that write IO can be coalesced prior to writing to the QLC layer. A reasonably large NVME TLC layer could store active data for as much as a week prior to writing it to the QLC layer, significantly decreasing the likelihood of the need to re-write data once on QLC, which extends the life of the QLC drive.
The possibilities that a TLC and QLC storage architecture open up is significant. QLC has the opportunity to enable customers to easily cost justify putting all production workloads on flash. Active Archive is another use case for the combination, with QLC storing dormant data, response to queries become instant and lessen the reason to keep all data on primary storage. A TLC/QLC combination can even extend the use case to backup storage where capabilities like instant recovery demand higher performing data protection storage.
Micron has long been a leader in providing flash technology to the market. The value that the company adds at the controller layer to optimize flash performance is a key differentiator. The combination of NVMe TLC and SATA QLC opens the door for a flash only data center expanding the use cases to even backup and archive. Most importantly the technology to automatically and seamlessly implement these strategies is available today.