Category: Virtualization

One of my readers sent me this question:

I'm researching NFV/SDN and wonder if the software L2 switches support spanning tree.

TL&DR: Some do, some don’t.

I love listening to the Datanauts podcast (Ethan and Chris are fantastic hosts), starting from the very first episode (hyper-converged infrastructure) in which Chris made a very valid comment along the lines of “with the hyper-converged infrastructure it’s possible to get so many things done without knowing too much about any individual thing…” and I immediately thought “… and what happens when it fails?”

Last year I claimed that you don’t need more than two switches in your data center (I’ll run a presentation on the same topic in a few days), but focused exclusively on the networking side of the equation.

Iwan Rahabok recently published a great blog post describing the compute- and storage parts of it. His conclusion: 1000 VM per rack is perfectly realistic.

I had fun times participating in a discussion focused on whether it makes sense to deploy OTV+LISP in a new data center deployment. Someone quickly pointed out the elephant in the room:

How many LISP VM mobility installs has anyone on this list been involved with or heard of being successfully deployed? How many VM mobility installs in general, where the VMs go at least 1,000 miles? I'm curious as to what the success rate for that stuff is.

I think we got one semi-qualifying response, so I made it even simpler ;)

During my recent SDN workshops I encountered several networking engineers who use Nexus 1000V in their data center environment, and some of them claimed their organization decided to do so to ensure the separation of responsibilities between networking and virtualization teams.

There are many good reasons one would use Nexus 1000V, but the one above is definitely not one of them.

When I wrote my stretched VSAN post, I thought VSAN uses asynchronous replication across WAN. Duncan Epping quickly pointed out that it uses synchronous replication, and I fixed the blog post.

The “What about latency?” question immediately arose somewhere in my subconscious, but before I could add that thought to the blog post, Anders Henke wrote a lengthy comment that totally captured what I was thinking, so I’m including it in its entirety:

Pirmin Sidler read the stretched VSAN blog posts by Duncan Epping (intro, HA/DRS considerations, demo) and asked me what I think about stretched VSAN considering my opinions on long-distance vMotion.

TL&DR answer: it makes way more sense than long-distance vMotion. However…

In the Can Virtual Routers Compete with Physical Hardware blog post I mentioned that SSL termination remains one of the few bastions of hardware acceleration.

Based on the comment made by RPM, it looks like I was wrong.

Here’s his reasoning:

Most people casually involved with virtual appliances and network function virtualization (NFV) believe that replacing Linux TCP/IP stack with user-mode packet forwarding (example: Intel’s DPDK) boosts performance from meager 1 Gbps to tens of gigabits (and thus makes hardware forwarding obsolete).

Having data points is always better than having opinions; today let’s look at Receiving 1 Mpps with Linux TCP/IP Stack blog post.

2015-07-18: The blog post was updated based on feedback by Kristian Larsson.

At least a dozen engineers sent me emails or tweets mentioning Project Calico in the last few weeks – obviously the project is getting some real traction, so it was high time to look at what it’s all about.

TL&DR: Project Calico is yet another virtual networking implementation that’s a perfect fit for a particular use case, but falters when encountering the morass of edge cases.