Jumbo frames and the risks involved

Even though the jumbo frame and the possible gain and risk trade-offs discussion is not new, we found ourselves discussing it yet again. Because we had different opinions, it seems like a good idea to elaborate on this topic.

Let’s have a quick recap on what jumbo frames actually are. Your default MTU (Maximum Transmission Unit) for a ethernet frame is 1500. A MTU of 9000 is referred to as a jumbo frame.

Jumbo frames or 9000-byte payload frames have the potential to reduce overheads and CPU cycles.

Typically, jumbo frames are considered for IP storage networks or vMotion networks. A lot of performance benchmarking is already described on the web. It is funny to see a variety of opinions whether to adopt jumbo frames or not. Check this blogpost and this blogpost on jumbo frames performance compared to a standard MTU size. The discussion if ‘jumbo frames provide a significant performance advantage’ is still up in the air.

There are other techniques to improve network throughput and lower CPU utilization next to jumbo frames. A modern NIC will support the Large Segment Offload (LSO) and Large Receive Offload (LRO) offloading mechanisms. Note: LSO is also referenced as TSO (TCP Segmentation Offload). Both are configurable. LSO/TSO is enabled by default if the used NIC hardware supports it. LRO is enabled by default when using VMXNET virtual machine adapters.

Risks?

Let’s put the performance aspects aside, and let us look into the possible risks involved when implementing jumbo frames. The thing is, in order to be effective, jumbo frames must be enabled end to end in the network path. The main risk when adopting jumbo frames, is that if one component in the network path is not properly configured for jumbo frames, a MTU mismatch occurs.
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Stretched cluster with NSX

Last NLVMUG I was talking about stretched clusters. My presentation elaborated somewhat on how VMware NSX can help you deal with challenges that arise when deploying a stretched cluster solution. In this blogpost I want to have a closer look at this specific topic.

A quick understanding about what a stretched cluster solution actually is; it is a vSphere cluster configured in one vCenter instance containing an equal number of hosts from both sites. This allows for disaster avoidance (vMotion) and disaster recovery (vSphere HA) between two geographical separated sites. From the backend infrastructure perspective, your (synchronous replicated) storage and network solutions must span both sites.

Looking into network designs used for stretched clusters, you will typically face challenges like:

  • How do you design for VM mobility over 2 sites, requiring Layer-2 networks between the 2 sites?
  • Stretched Layer-2 networks (VLANs) introduce a higher risk of failure (think Layer-2 loops).
  • How to properly segment applications and/or tenants (customers/business units)?
  • Netwerk flows. What about your egress and ingress connections?

Let’s begin with how a VMware NSX install-base could look like if it is deployed within stretched cluster infrastructure.

Stretched cluster with NSX architecture

A stretched cluster with VMware NSX could look like the following logical overview.
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VCP-NV exam experience

Ending the year on a high!! Today Rutger and I passed the VMware Certificed Professional – Network Virtualization (VCP-NV) exam!! Robert will surely follow soon. 🙂
We had a rather small time frame to successfully pass VCP-NV because as of January 2015 we want full focus on VCDX-DCV. So it had to happen in 2014.

Although we didn’t have a great deal of hands-on experience (yet) with VMware NSX, we were able to pass the exam after a steep learning curve following our NSX deepdive session at VMware along with some really good documentation and blogposts on the matter… not to mention the VMware’s HOL labs!

vcpNV

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Welcome!

Welcome to Cloudfix, our blog!!

We recently decided to start this blog. We are still setting things up and shuffling a bit with the layout.
Shouldn’t take long now for us to start sharing and collaborating.

What makes us different from other blogs is that we are a bunch of guys participating in one blog rather than we all have our own! This should be good for our visitors; to have different perspectives on technologies we encounter. And because we all have our own package of experience, our blog posts should be diverse.

We hope we can welcome you as a regular visitor!!

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