Click here to close now.

Welcome!

Related Topics: SDN Journal, Java IoT, Linux Containers, Containers Expo Blog

SDN Journal: Blog Post

There Is Cost Per Port and Then There Is Cost Per Port…

I let you do the math on the cost of that infrastructure. And the installation. And the maintenance

Earlier this week, Ethan Banks wrote a very nice article about Mellanox’s dual spine and leaf network in support of a large amount 10GbE access ports. After describing the scaled up network design, he reviews 8 observations about the design, not to point out good or bad, but merely to point out specific points to consider. Fully coincidental (Ethan lives close to us, but I am pretty sure he cannot peek through our windows) we had gone through a similar exercise this week, documenting the choices and limitations of spine and leaf networks. And as always, the conclusions are not ones of right or wrong, more of awareness of choices and consequences.

The Mellanox design Ethan describes employes an extra spine layer, we have seen and heard the same from Arista and others, some calling it a spine-spine or similar. Nitpicking perhaps, but adding a spine layer to a spine and leaf network and still calling it a spine and leaf network is like adding a docking station, screen and keyboard to a phone and still calling it a phone. It’s a computer that can make calls. And a spine and leaf network with an extra spine is a fat tree.

Ethan points out in his first few points that the sheer amount of cables and optics is astonishing. Let me try and put some numbers around that statement. If you build an approximate 3:1 oversubscribed spine and leaf network out of generic switches, I would probably use a Trident2 based ToR switch with 48 SFP+/10GbE ports and 6 QSFP/40GbE ports. The 48 ports should serve most rack deployments with single homed servers, only really dense or heavily multi homed servers would need more ports and I will use 4 of the QSFP ports to connect to my spine. That leaves 2 QSFPs on each leaf to be used for extra access ports, at the cost of some oversubscription. Or if I wanted I could use these as extra spine connections, lowering my oversubscription to 2:1. As a spine, and staying away from chassis based systems, I would pick a 32xQSFP/40GbE switch.

The largest spine and leaf I could build out of this combination is one that contains 16 spine switches and 96 leaf switches. In a spine and leaf I need to connect each leaf to each spine and I have the equivalent of 16x10GbE to use out of each leaf, which I can connect to at best 16 spines. With each spine receiving 1x10GbE from each leaf, I can build out to 96 leafs to fill out my 32xQSFP or 96x10GbE equivalent spine switch capacity. 96 Leaf switches give me 4608 10GbE access ports at 3:1 oversubscription, 5376 at a slightly worse oversubscription if I use the extra QSFP ports on my leaf switches. To support these 5376 access ports, I need 3584 10GbE fabric ports: 16 each from 96 leaf switches plus 32×4 from each spine. That means 1792 switch interconnect cables. And 3584 10GbE short reach optics, because the vast majority of connections between spines and leafs is likely to be at a distance that DAC cables cannot cover (not considering the fact that most high density 10GbE switches are designed without PHYs, limiting the use of passive cables to usually 5m or less).

I let you do the math on the cost of that infrastructure. And the installation. And the maintenance. And the sheer complexity of running a 10GbE from each leaf to each spine. If you want to reduce some of this complexity, you can switch to using 40GbE/QSFPs between the leafs and spines, but by doing so you have reduced the maximum size of the network. Each leaf will now contribute 1 QSFP worth of interconnect to each spine, to a 32xQSFP spine can only support 32 leaf switches, or 1536 10GbE access ports (1792 if you use the 2 extra leaf QSFP ports). And you probably noticed that I left no room on the spine switches to actually leave this spine and leaf network to the rest of the network infrastructure. Taking a few QSFPs for that will reduce the size of the network more.

Even in the spine, spine and leaf network (or spine, leaf and ToR in Mellanox terminology) the amount of cabling between the ToR (someone explain why that is not the leaf of the network?) and the aggregation leaf may be reduced, the cabling between their aggregation leaf and spine still follows the same model as above.

We often focus on the cost of switches and the derived cost per port. Of course the cost per port is important, but don’t fool yourself by taking the cost of a switch and dividing it by the number of ports it supports. It makes for great quotes in press releases, but the actual cost for that port is way higher the moment you add in the overhead required to connect that port to the rest of the network. And for spine and leaf networks, the cost of the rest of the network has a very large portion of cables and optics. Even for reasonably priced optics, that piece of the infrastructure is likely going to cost more than the cost of the spine switches together. Even when you create one of these multispined animals…

[Today's fun fact: The human spine contains 120 muscles and approximately 220 individual ligaments.]

The post There is cost per port and then there is cost per port… appeared first on Plexxi.

Read the original blog entry...

More Stories By Marten Terpstra

Marten Terpstra is a Product Management Director at Plexxi Inc. Marten has extensive knowledge of the architecture, design, deployment and management of enterprise and carrier networks.

Latest Stories
The enterprise market will drive IoT device adoption over the next five years. In his session at @ThingsExpo, John Greenough, an analyst at BI Intelligence, division of Business Insider, analyzed how companies will adopt IoT products and the associated cost of adopting those products. John Greenough is the lead analyst covering the Internet of Things for BI Intelligence- Business Insider’s paid research service. Numerous IoT companies have cited his analysis of the IoT. Prior to joining BI In...
"We have been in business for 21 years and have been building many enterprise solutions, all IT plumbing - server, storage, interconnects," stated Alex Gorbachev, President of Intelligent Systems Services, in this SYS-CON.tv interview at 16th Cloud Expo, held June 9-11, 2015, at the Javits Center in New York City.
"ciqada is a combined platform of hardware modules and server products that lets people take their existing devices or new devices and lets them be accessible over the Internet for their users," noted Geoff Engelstein of ciqada, a division of Mars International, in this SYS-CON.tv interview at @ThingsExpo, held June 9-11, 2015, at the Javits Center in New York City.
The time is ripe for high speed resilient software defined storage solutions with unlimited scalability. ISS has been working with the leading open source projects and developed a commercial high performance solution that is able to grow forever without performance limitations. In his session at Cloud Expo, Alex Gorbachev, President of Intelligent Systems Services Inc., shared foundation principles of Ceph architecture, as well as the design to deliver this storage to traditional SAN storage co...
Countless business models have spawned from the IaaS industry. Resell Web hosting, blogs, public cloud, and on and on. With the overwhelming amount of tools available to us, it's sometimes easy to overlook that many of them are just new skins of resources we've had for a long time. In his General Session at 16th Cloud Expo, Phil Jackson, Lead Technology Evangelist at SoftLayer, broke down what we've got to work with and discuss the benefits and pitfalls to discover how we can best use them to d...
"We have seen the evolution of WebRTC right from the starting point to what it has become today, that people are using in real applications," noted Dr. Natasha Tamaskar, Vice President and Head of Cloud and Mobile Strategy and Ecosystem at GENBAND, in this SYS-CON.tv interview at WebRTC Summit, held June 9-11, 2015, at the Javits Center in New York City.
Enterprises are turning to the hybrid cloud to drive greater scalability and cost-effectiveness. But enterprises should beware as the definition of “policy” varies wildly. Some say it’s the ability to control the resources apps’ use or where the apps run. Others view policy as governing the permissions and delivering security. Policy is all of that and more. In his session at 16th Cloud Expo, Derek Collison, founder and CEO of Apcera, explained what policy is, he showed how policy should be arch...
The 3rd International WebRTC Summit, to be held Nov. 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA, announces that its Call for Papers is now open. Topics include all aspects of improving IT delivery by eliminating waste through automated business models leveraging cloud technologies. WebRTC Summit is co-located with 15th International Cloud Expo, 6th International Big Data Expo, 3rd International DevOps Summit and 2nd Internet of @ThingsExpo. WebRTC (Web-based Real-Time Com...
Internet of Things (IoT) will be a hybrid ecosystem of diverse devices and sensors collaborating with operational and enterprise systems to create the next big application. In their session at @ThingsExpo, Bramh Gupta, founder and CEO of robomq.io, and Fred Yatzeck, principal architect leading product development at robomq.io, discussed how choosing the right middleware and integration strategy from the get-go will enable IoT solution developers to adapt and grow with the industry, while at th...
It is one thing to build single industrial IoT applications, but what will it take to build the Smart Cities and truly society-changing applications of the future? The technology won’t be the problem, it will be the number of parties that need to work together and be aligned in their motivation to succeed. In his session at @ThingsExpo, Jason Mondanaro, Director, Product Management at Metanga, discussed how you can plan to cooperate, partner, and form lasting all-star teams to change the world...
SYS-CON Events announced today that Harbinger Systems will exhibit at SYS-CON's 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Harbinger Systems is a global company providing software technology services. Since 1990, Harbinger has developed a strong customer base worldwide. Its customers include software product companies ranging from hi-tech start-ups in Silicon Valley to leading product companies in the US a...
The 4th International Internet of @ThingsExpo, co-located with the 17th International Cloud Expo - to be held November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA - announces that its Call for Papers is open. The Internet of Things (IoT) is the biggest idea since the creation of the Worldwide Web more than
SYS-CON Events announced today that ProfitBricks, the provider of painless cloud infrastructure, will exhibit at SYS-CON's 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. ProfitBricks is the IaaS provider that offers a painless cloud experience for all IT users, with no learning curve. ProfitBricks boasts flexible cloud servers and networking, an integrated Data Center Designer tool for visual control over the...
"We got started as search consultants. On the services side of the business we have help organizations save time and save money when they hit issues that everyone more or less hits when their data grows," noted Otis Gospodnetić, Founder of Sematext, in this SYS-CON.tv interview at @DevOpsSummit, held June 9-11, 2015, at the Javits Center in New York City.
"CenturyLink brings a full suite of services to the table and that enables us to be an IT service provider," explained Jeff Katzen, Director of the Cloud Practice at CenturyLink, in this SYS-CON.tv interview at 16th Cloud Expo, held June 9-11, 2015, at the Javits Center in New York City.