Flash Diversity: High Capacity Drives from Nimbus and Micron

Flash Diversity: High Capacity Drives from Nimbus and Micron

Chris EvansAll-Flash Storage

The desire to provide cheaper and greater capacity storage devices knows no bounds and has been a focus of the industry for the last 60 years.  Following on from Seagate’s 60TB “concept” flash drive, we now have two vendors selling 50TB OEM flash drives from Nimbus Data.  Let’s put that into context – the largest capacity hard drive is currently 12TB (7.2K RPM capacity drive from HGST/Western Digital).  Flash vendors are now making drives with 5x the capacity in the same 3.5″ form factor.  Admittedly these new drives will be prohibitively expensive for general use cases, but with the introduction of QLC, the margin of gap between HDD and SSD per GB pricing could close further.

Nimbus 50TB

It’s fair to say that Nimbus Data has had a chequered history.  I first was introduced to the company at a Tech Field Day event back in 2012 (in fact Storage Field Day 1) and one memory from that presentation was that Nimbus had developed their own drives for use within the array they were demonstrating.  See the photo here, which I think was an 800GB drive.  It seems that although the array business wasn’t as successful, perhaps there was some IP in the SSD development, as Nimbus has now produced 50TB drives that are being OEM’d through Viking and Smart Modular (you may remember them from the NVDIMM market).

So what are the specifications of these devices?  Smart’s Osmium Drive quotes capacities of 25 and 50TB, 6Gb/s SAS connectivity, based on MLC NAND.  Sequential read is 472MB/s, write is 325MB/s with 58K random read IOPS and 15K random write IOPS.  There are no quoted latency figures.  The performance figures aren’t great (compare to the Micron ones in a moment), especially the write numbers, so this is clearly a capacity flash drive (if such a term exists) rather than a performance one.  As a result, pricing should reflect this, although I’ve seen no specifics on the cost.

Digging deeper into the technology, Nimbus claims the 50TB “ExaDrive” uses mulitple custom ASICs to handle the functions that would normally be done by a drive controller, although there is also an intelligent “flash controller” integrated into the device.  The ASICs manage error correction, while the controller handles standard features like wear levelling.  Nimbus are claiming 500TB drives within three years, which seems massively ambitious.  A few things stand out as potential issues.  First, using SAS as the interface protocol will continue to be a problem compared to NVMe.  Although throughput with 12Gb/s SAS would improve things, the parallelism of SAS isn’t there compared to NVMe and as drive capacities increase, individual devices need to be capable of handling dozens if not hundreds of parallel requests – especially with 500TB capability.

Second is the media being used, which is quoted as MLC.  Most vendors are moving to TLC and QLC is just around the corner.  For capacity drives with lower performance specs, TLC and QLC will be the only way to get a reasonable price/performance ratio.  So ExaDrive needs quickly to move to these technologies.  I can’t find any details on the Nimbus website of any partnerships with the NAND manufacturers.  It seems to me that this is an essential part of any ongoing strategy.  I’d like to see a roadmap for the adoption of TLC, QLC and NVMe, because this is where the future of large capacity drives will be.

Micron 9200

Yesterday Micron announced new 9200 series drives.  Although not scaling as high, the 9200 does come in three models (Eco, Pro and Max), with up to 11TB of capacity (Eco model).  The range of capacities reflects the use of FlexPro and FlexCapacity architectures, giving the ability to offset capacity for extended endurance.  All models are NVMe based, either using the U.2 or AIC format (as a half-height, half-length card).  Performance figures quote up to 4.6GB/s (sequential read) and 3.8GB/s (write) with (the magic) one million random read IOPS or up to 270,000 random write IOPS in the MAX model (across the range, figures range from 95,000 to 270,000).

Although not quoted on the specification sheet, I validated some additional information with Micron.  The 9200 is a TLC product using 384Gb/s 32-layer chips.  Read latency is around 150μs and 30μs for writes.  The three model types target different use cases – ECO for read, PRO for mixed workloads and MAX for write intensive.  MAX devices have more than double the endurance figures (petabytes written) for ECO, for example.

The Architect’s View®

It would be unreasonable to directly compare Micron’s new drives with the capacity ones from Nimbus, however we can see that in all practical senses the limits of capacity seen in hard drives are well and truly exceeded by flash.  In order to get capacity, Nimbus have been required to use a larger form-factor, with a higher power footprint, although to be fair at around 15W, it’s not that bad.  In the performance market, drive capacities around 10TB are becoming the norm.  With the introduction of QLC, the capacity flash market is set to diversify even further.  In fact Samsung has already pre-announced a 128TB QLC drive at the Flash Memory Summit.

There’s an ever increasing range of products based over three axes – price, performance and capacity, with endurance in there somewhere as even a fourth dimension.  From a media perspective we are on the cusp of hybrid all-flash arrays, with more choices than ever for HCI solutions.  Solid state media is getting really interesting and I pity the HDD vendors who haven’t moved fully with the times.

Further Reading

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