Keeping up with changes in the world of container storage is not easy. That’s why the SNIA Cloud Storage Technologies Initiative invited expert Keith Hudgins of Docker for a live webcast, “What’s New in Container Storage.” I encourage you to watch it on-demand. It’s well worth the approximately half-hour investment to get up to speed on container storage.
As promised during the live event, here are answers to the questions we received:
Q. How does the new Container Storage Interface fit in here?
A. Container Storage Interface (CSI) is one of the three persistent storage interfaces for Kubernetes. It’s also gaining a bit of traction for non-Kubernetes use as well: Pivotal and Mesos have announced their intention to use the API for support for volume use. You can learn more at the CSI main project page.
Q. Where does LXD/LXC fit into this discussion?
A. Not very well – LXC technology was used in earlier versions of Docker prior to Docker Engine 1.10. There is some provision under LXC for both persistent volumes and overlay, but I’m honestly not that familiar with the pluggable APIs for that container tech. Here’s a link to some docs for the LXD persistent storage interface.
Q. How does hardware-RAID created volumes play a role in Kubernetes? Do the hardware RAID volumes need an out-of-tree plugin for Kubernetes persistent volume?
A. Hardware RAID devices can provide volumes for containers running under Kubernetes. Like any installation, the method you use will depend on your requirements. You can use basic, in-tree drivers for most cases. Kubernetes has built-in support for NFS and iSCSI. Depending on needs, you can also build a custom driver using FlexVolume or CSI.
Q. Are there plans to add Docker support for persistent me
A.It’s a very new technology – we’re interested in the applications but it’s new. We’re waiting to see how the market matures.
Q. Is FlexVolume persistent storage?
A. Yes, absolutely. FlexVolume is one of the three persistent storage APIs available for use with Kubernetes. For deeper info on how to build FlexVolume plugins, take a look at these links:
You can learn more about container storage in the other three container webcasts the CSTI has hosted:
If you have questions, please leave comments in this blog. Happy viewing!
Mark Carlson (MC): SNIA does not just sit back and dream up work to do, but rather relies on industry input and requirements. A great example of how SNIA work is created is the 2018 launch of the Computational Storage Technical Work Group (TWG). It all started at the Flash Memory Summit industry event with a simple Birds-of-a-Feather on a thing called “computational storage”. Interest definitely was high – the room was packed - and the individuals assembled decided to use SNIA as the vehicle to do definition and standardization of this new concept.
SOS: What made them choose SNIA?
MC: The industry views SNIA as a place where they can come to get agreement on technical issues. SNIA is committed to developing and promoting standards in the broad and complex fields of digital storage and information management to allow solutions to be more easily produced. Technical Work Groups (TWGs) are collaborative technical groups within the SNIA that work on specific areas of technology development.
In the case of computational storage, it was clear that the industry saw SNIA as a catalyst to get things off and running with computational storage in the standards world because…six months after FMS we have a new Technical Work Group with 90 individuals from 30 member companies starting their work and evangelizing computational storage at events like March’s OCP Summit.
SOS: What are some of the changing storage industry trends that might create a need for new SNIA efforts?
MC: We see some exciting activity in the areas of composable infrastructure, next generation fabrics, and new data center innovations. Standard computer architectures in data centers today are essentially servers acting as the building blocks for assembling data center sized solutions. But imagine if CPUs, memory, storage, and networks were individual components on next generation fabrics, making more granular building blocks. The definition then of what a server is would be an assemblage on the fly of these components. Scalability of any individual platform instance would become a matter of combining sufficient components for the task.
SOS: What role would SNIA play?
MC: Composable infrastructure will now need to be managed in a different way than when using servers as a building block. Rather than having a single point of management for multiple components in a box, management now needs to be component-based and handled by the components themselves. Redfish from the DMTF is already architected for this very issue of scale out and SNIA’s Swordfish is continuing to extend this into storage architectures.
SNIA is already a pioneer in the area of storage management, and anticipating this coming possible disruption by moving its standards to modern protocols with alliance partners like DMTF and NVM Express. DMTF Redfish and SNIA Swordfish are examples of this work where Object Drive and other work items create a Redfish profile for NVMe drives. NVMe drives will be a storage component and a peer of the CPU either attached to the host or not attached and outside the box.
Next generation fabrics are enabling these composable infrastructures, making new data center innovation possible. But the new fabrics themselves need to be managed as well.
SOS: Where can folks learn about these activities in person?
MC: Check out the Computational Storage Birds-of-a-Feather at USENIX FAST this week. In March, SNIA will present Persistent Memory, including a PM Programming Tutorial and Hackathon at the Non Volatile Memory Workshop at UC San Diego; Computational Storage presentations at OCP Summit; and NVM alliance activities at NVM Annual Members Meeting and Developer Day.
SOS: Exciting news indeed! Thanks, Mark, and we’ll look forward to seeing SNIA at upcoming events.
Hyperconverged infrastructures (also known as “HCI”) are designed to be easy to set up and manage. All you need to do is add networking. In practice, the “add networking” part has been more difficult than most anticipated. That’s why the SNIA Networking Storage Forum (NSF) hosted a live webcast “
/TCP Means to Networked Storage
Leave it to Rob Peglar, SNIA Board Member and the MC of SNIA’s 7th annual 
This is a 10:1 oversubscription ratio; the "fan-in" part refers to the number of host bandwidth in comparison to the target bandwidth.
Block storage protocols like Fibre Channel, FCoE, and iSCSI have much lower fan-in ratios than file storage protocols such as NFS, and deterministic storage protocols (like FC) have lower than non-deterministic (like iSCSI). The true arbiter of what the appropriate fan-in ratio is determined by the application. Highly transactional applications, such as databases, often require very low ratios.
Q. If there's a mismatch in the MTU between server and switch will the highest MTU between the two get negotiated or else will a mismatch persist?
A. No, the lowest value will be used, but there's a caveat to this. The switch and the network in the path(s) can have MTU set higher than the hosts, but the hosts cannot have a higher MTU than the network. For example, if your hosts are set to 1500 and all the network switches in the path are set to 9k, then the hosts will communicate over 1500.
However, what can, and usually does, happen is someone sets the host(s) or target(s) to 9k but never changes the rest of the network. When this happens, you end up with unreliable or even loss of connectivity. Take a look at the graphic below:
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