VMworld Europe update – NVMeoF

I’m attending VMworld in Barcelona Spain this week delivering a session on NVM and NVMe, the same one I delivered in Las Vegas in fact…well almost. Our development team has made some great progress on the next generation of connectivity, NVMeoF or NVMe over fabric, so I am including a demonstration on that. To that end, our PowerMax team wrote their own blog post on the developments which you can read here and then hop back over for some more background.

So the post talks about NVMeoF as well as SCM or storage class memory, but I wanted to take a step back as I don’t think I’ve written much about NVM and NVMe. So what is NVM and NVMe and why are there two of them? NVM stands for non-volatile (media) memory. This is the media itself such as NAND-based flash or as I just mentioned, storage class memory. If you run a VMAX with flash you have NVM. Now NVMe or non-volatile memory express is a set of standards which define a PCI Express (PCIe) interface used to efficiently access data storage volumes on NVM. The standards were developed by a consortium of a bunch of companies, including Dell. NVMe is a moving target as new specifications are always in flux. The first spec was a simple command set of about a dozen, but more and more features are being added in each spec, e.g. multipath, compare and write – locking (ATS). NVMe is all about concurrency, parallelism, and scalability to push performance. It replaces the other SCSI protocols which were never designed to work with the speeds of flash. Our PowerMax is an all-NVMe box so it benefits from this increase in speed, however there is a second part of the NVMe story and that is the network.

If we look at NVMe in its simplest form, it is a server with local NVMe storage. No network is required. VMware supports such servers with the NVMe interface and will recognize those disks as local NVMe. As you may recall, VMware even has an NVMe controller for vmdks placed on those disks (though you can use the controller with non-NVMe). But how do we get VMware to recognize NVMe disks on a SAN since we must get to the storage over a traditional IP or Fibre Channel network? Well right now you don’t. That is where NVMeoF comes into play.

NVMe over fabric defines a common storage architecture for accessing the NVMe block storage protocol over a storage network. This means going from server to SAN, including a front-end interface to NVMe storage. But didn’t I just say that PowerMax is an NVMe box? Yep, all the way up to where it gets plugged into the network. Since NVMeoF isn’t available yet, the front-end interfaces remain the same which among other things means that all the nice benefits of VMware like VAAI still work on the array. NVMeoF will come in a bunch of flavors. Two of the main ones are RDMA – which include Infiniband, RoCE and iWARP – and Fibre Channel or FC-NVMe. As FC is the predominant technology for our customers, we are starting with FC-NVMe.

Here is a simple representation of NVMeoF connectivity.

At first glance, the idea that there will be a new network required for NVMe might be disconcerting, if only for the cost of such an endeavor. So let me put your mind at rest, you won’t need to change a thing. Huh? Well FC-NVMe right? It will use your existing Fibre Channel network. Not only that, but FC-NVMe can co-exist with your traditional FC. I’m sure that got your attention. This is going to allow a seamless transition from one to the other. And what if you continue to run other non-VMware applications that need regular FC? No problem at all. In fact, for VMware, you can present storage on both traditional FC and FC-NVMe, then Storage vMotion VMs on FC to new datastores on FC-NVMeoF. Therefore moving to FC-NVMe can be accomplished with no downtime. And that is where the demo comes in. For VMworld Europe I created this tech preview demo which shows moving a VM between the two different interfaces of FC and FC-NVMe. In the video I go back and forth between the datastores just to show it is not a one-way street.

Note the video is a tech preview, showing unreleased Dell EMC and VMware hardware and software.

You probably noticed in the video that I included SCM or storage class memory, the newest NVM technology. These drives are faster than NAND flash, though a good deal more expensive. Because the PowerMax has built-in machine learning, you won’t need a lot of SCM to start, however. The array will automatically determine what data should be moved to SCM to get the best performance for your applications. Over time, just like with the transition to flash, SCM will come down in price. By the way, adding front-end access for FC-NVMe and SCM drives to the PowerMax will be non-disruptive.

When can you expect to see FC-NVMe on PowerMax? Next year – 2019 the future is coming. I cannot of course speak to VMware’s release schedule to support FC-NVMe so be sure to check out their website for updates.


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