QoM1610: Will NVMe over Fabric GA in enterprise AFA by Oct’2017

NVMeNVMe over fabric (NVMeoF) was a hot topic at Flash Memory Summit last August. Facebook and others were showing off their JBOF (see my Facebook moving to JBOF post) but there were plenty of other NVMeoF offerings at the show.

NVMeoF hardware availability

When Brocade announced their Gen6 Switches they made a point of saying that both their Gen5 and Gen6 switches currently support NVMeoF protocols. In addition to Brocade’s support, in Dec 2015 Qlogic announced support for NVMeoF for select HBAs. Also, as of  July 2016, Emulex announced support for NVMeoF in their HBAs.

From an Ethernet perspective, Qlogic has a NVMe Direct NIC which supports NVMe protocol offload for iSCSI. But even without NVMe Direct, Ethernet 40GbE & 100GbE with  iWARP, RoCEv1-v2, iSCSI SER, or iSCSI RDMA all could readily support NVMeoF on Ethernet. The nice thing about NVMeoF for Ethernet is not only do you get support for iSCSI & FCoE, but CIFS/SMB and NFS as well.

InfiniBand and Omni-Path Architecture already support native RDMA, so they should already support NVMeoF.

So hardware/firmware is already available for any enterprise AFA customer to want NVMeoF for their data center storage.

NVMeoF Software

Intel claims that ~90% of the software driver functionality of NVMe is the same for NVMeoF. The primary differences between the two seem to be the NVMeoY discovery and queueing mechanisms.

There are two fabric methods that can be used to implement NVMeoF data and command transfers: capsule mode where NVMe commands and data are encapsulated in normal fabric packets or fabric dependent mode where drivers make use of native fabric memory transfer mechanisms (RDMA, …) to transfer commands and data.

12679485_245179519150700_14553389_nA (Linux) host driver for NVMeoF is currently available from Seagate. And as a result, support for NVMeoF for Linux is currently under development, and  not far from release in the next Kernel (I think). (Mellanox has a tutorial on how to compile a Linux kernel with NVMeoF driver support).

With Linux coming out, Microsoft Windows and VMware can’t be far behind. However, I could find nothing online, aside from base NVMe support, for either platform.

NVMeoF target support is another matter but with NICs/HBAs & switch hardware/firmware and drivers presently available, proprietary storage system target drivers are just a matter of time.

Boot support is a major concern. I could find no information on BIOS support for booting off of a NVMeoF AFA. Arguably, one may not need boot support for NVMeoF AFAs as they are probably not a viable target for storing App code or OS software.

From what I could tell, normal fabric multi-pathing support should work fine with NVMeoF. This should allow for HA NVMeoF storage, a critical requirement for enterprise AFA storage systems these days.

NVMeoF advantages/disadvantages

Chelsio and others have shown that NVMeoF adds ~8μsec of additional overhead beyond native NVMe SSDs, which if true would warrant implementation on all NVMe AFAs. This may or may not impact max IOPS depending on scale-ability of NVMeoF.

For instance, servers (PCIe bus hardware) typically limit the number of private NVMe SSDs to 255 or less. With an NVMeoF, one could potentially have 1000s of shared NVMe SSDs accessible to a single server. With this scale, one could have a single server attached to a scale-out NVMeoF AFA (cluster) that could supply ~4X the IOPS that a single server could perform using private NVMe storage.

Base level NVMe SSD support and protocol stacks are starting to be available for most flash vendors and operating systems such as, Linux, FreeBSD, VMware, Windows, and Solaris. If Intel’s claim of 90% common software between NVMe and NVMeoF drivers is true, then it should be a relatively easy development project to provide host NVMeoF drivers.

The need for special Ethernet hardware that supports RDMA may delay some storage vendors from implementing NVMeoF AFAs quickly. The lack of BIOS boot support may be a minor irritant in comparison.

NVMeoF forecast

AFA storage systems, as far as I can tell, are all about selling high IOPS and very-low latency IOs. It would seem that NVMeoF would offer early adopter AFA storage vendors a significant performance advantage over slower paced competition.

In previous QoM/QoW posts we have established that there are about 13 new enterprise storage systems that come out each year. Probably 80% of these will be AFA, given the current market environment.

Of the 10.4 AFA systems coming out over the next year, ~20% of these systems pride themselves on being the lowest latency solutions in the market, and thus command high margins. One would think these systems would be the first to adopt NVMeoF. But, most of these systems have their own, proprietary flash modules and do not use standard (NVMe) SSDs and can use their own proprietary interface to their proprietary flash storage. This will delay any implementation for them until they can convert their flash storage to NVMe which may take some time.

On the other hand, most (70%) of the other AFA systems, that currently use SAS/SATA SSDs, could boost their IOP counts and drastically reduce their IO  response times, by implementing NVMe SSDs and NVMeoF. But converting SAS/SATA backends to NVMe will take time and effort.

But, there are a select few (~10%) of AFA systems, that already use NVMe SSDs in their AFAs, and for these few, they would seem to have a fast track towards implementing NVMeoF. The fact that NVMeoF is supported over all fabrics and all storage interface protocols make it even easier.

Moreover, NVMeoF has been under discussion since the summer of 2015, which tells me that astute AFA vendors have already had 18+ months to develop it. With NVMeoF host drivers & hardware available since Dec. 2015, means hardware and software exist to test and validate against.

I believe that NVMeoF will be GA’d within the next 12 months by at least one enterprise AFA system. So my QoM1610 forecast for NVMeoF is YES, with a 0.83 probability.





Flash’s only at 5% of data storage

7707062406_6508dba2a4_oWe have been hearing for years that NAND flash is at price parity with disk. But at this week’s Flash Memory Summit, Darren Thomas, VP Storage BU, Micron said at his keynote that NAND only store 5% of the bits in a data center.

Darren’s session was all about how to get flash to become more than 5% of data storage and called this “crossing the chasm”. I assume the 5% is against yearly data storage shipped.

Flash’s adoption rate

Darren, said last year flash climbed from 4% to 5% of data center storage, but he made no mention on whether flash’s adoption was accelerating. According to another of Darren’s charts, flash is expected to ship ~77B Gb of storage in 2015 and should grow to about 240B Gb by 2019.

If the ratio of flash bits shipped to data centers (vs. all flash bits shipped) holds constant then Flash should be ~15% of data storage by 2019. But this assumes data storage doesn’t grow. If we assume a 10% Y/Y CAGR for data storage, then flash would represent about ~9% of overall data storage.

Data growth at 10% could be conservative. A 2012 EE Times article said2010-2015 data growth CAGR would be 32%  and IDC’s 2012 digital universe report said that between 2012 and 2020, data will double every two years, a ~44% CAGR. But both numbers could be talking about the world’s data growth, not just data center.

How to cross this chasm?

Geoffrey Moore, author of Crossing the Chasm, came up on stage as Darren discussed what he thought it would take to go beyond early adopters (visionaries) to early majority (pragmatists) and reach wider flash adoption in data center storage. (See Wikipedia article for a summary on Crossing the Chasm.)

As one example of crossing the chasm, Darren talked about the electric light bulb. At introduction it competed against candles, oil lamps, gas lamps, etc. But it was the most expensive lighting system at the time.

But when people realized that electric lights could allow you to do stuff at night and not just go to sleep, adoption took off. At that time competitors to electric bulb did provide lighting it just wasn’t that good and in fact, most people went to bed to sleep at night because the light then available was so poor.

However, the electric bulb  higher performing lighting solution opened up the night to other activities.

What needs to change in NAND flash marketing?

From Darren’s perspective the problem with flash today is that marketing and sales of flash storage are all about speed, feeds and relative pricing against disk storage. But what’s needed is to discuss the disruptive benefits of flash/NAND storage that are impossible to achieve with disk today.

What are the disruptive benefits of NAND/flash storage,  unrealizable with disk today.

  1. Real time analytics and other RT applications;
  2. More responsive mobile and data center applications;
  3. Greener, quieter, and potentially denser data center;
  4. Storage for mobile, IoT and other ruggedized application environments.

Only the first three above apply  to data centers. And none seem as significant  as opening up the night, but maybe I am missing a few.

Also the Wikipedia article cited above states that a Crossing the Chasm approach works best for disruptive or discontinuous innovations and that more continuous innovations (doesn’t cause significant behavioral change) does better with Everett Roger’s standard diffusion of innovation approaches (see Wikepedia article for more).

So is NAND flash a disruptive or continuous innovation?  Darren seems firmly in the disruptive camp today.


Photo Credit(s): 20-nanometer NAND flash chip, IntelFreePress’ photostream