Monday, December 28, 2009

So, what advatages are there to having a Cisco VSS configuration?

I've been in several discussions with clients who are trying to understand the benefit of Cisco VSS vs a Nexus 7k approach for new data center deployments. Cisco has some excellent information out there on differences between the two platforms but if you haven't been on the lookout to upgrade your network infrastructure you might have missed the discussion.

I think both the Cisco VSS and Nexus solutions address many of the frustrations that people who are building larger data centers with virtualization are looking for. Specifically, a way to get redundancy and high availability plus very large bandwidth into their server farms while not building out a massive layer 3 network which can cause limitations for virtualization solutions. One of the advantages for companies that are not doing virtualization (perhaps their applications require all the cpu and memory of the host server) is that the architecture works equally well for them.

Cisco has build some specific solutions around virtualization plus data center, this is their recent announcement of the UCS products. I am not going to bother discussing that in this post and if you want to know more about that I suggest reading Colin McNamara's blog - he covers it really well so no reason to repeat it here.

So why would you pick a Cisco VSS solution vs a Cisco Nexus solution. There isn't an obvious answer at first blush.

Here would be the short list of why VSS first. They would be:
1. Having staff who understand and are familiar with the Cisco 6500 series and support a lot of them already.
2. The requirement for having service modules in the solution, something VSS supports but Nexus does not.
3. Moving from an existing investment in 6500's with Sup720-10G's to a high available, redundant solution split across multiple chassis - gear reuse.
4. Want tight fault tolerance solutions with other Catalyst switching platforms.
5. Able to provide Multichassis EtherChannel (MEC) to downstream or upstream devices.

Here would be the short list of why Nexus first. They would be:
1. Running into throughput and performance problems with a 6500 solution at core or distribution. Especially due to service modules impacting performance.
2. Would like to move to having independent point devices for services like firewalling, load balancing, network analysis and wireless. Perhaps you like a different vendors load balancer or firewall product that run at much higher throughputs.
3. Moving to very high density 1 and 10G server solutions that can grow and scale for investment protection.
4. Moving to the next generation platform where Cisco will be investing research and dollars into.
5. Able to provide Multichassis EtherChannel (MEC) to downstream or upstream devices.

So, if you are building out a data center soon that will require a 5-7 year lifespan then I really suggest moving to the Nexus platform now. Cisco is making the pricing just as attractive as the 6500 series but you gain all the advantages of moving to the next generation of platform.

If your time horizon is shorter for changing out your data center network equipment then the Cisco 6500 VSS solution is a great transition product which allows the re-use of your 6500 chassis and investment in supervisors (if you have Sup720-10G's already) and service modules.

The reality is that you will likely have both within your data center if you are making reuse of service modules. You can then run those service modules in 6500 series with 10Gig to a core Nexus plaform with the 6500's running VSS MEC to the Nexus 7000's running vPC MEC.

Both solution will work to your downstream server farms for MEC and the VSS has been upgraded to support 512 Port-Channels in a single chassis, more than enough considering many servers are getting 4 x 1Gig ports or more channeled together to the network.
- Ed

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