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The hidden costs of virtualization part 2: Networking

Quoting TechTarget's SearchServerVirtualization.com

This is part two of a three part article written by David Marshall and Dan Knezevic.

Part one of this discussion on hidden virtualization costs went over the power and heat costs and the management concerns of virtualization. Now, in part two, we will turn our attention to networking issues and the problem of virtual machine sprawl. Part three will discuss licensing, performance and storage.

Networking issues

Virtualized servers have unique networking concerns. In a virtual network, you will see a larger than average number of IP addresses, more than usual subnets and VLANs, high packets per second, greater susceptibility to switch port problems, greater need to plan machine per host density and MAC address management issues.

  • IP addresses
    Depending on the density of virtual machines achieved per physical host, you will quickly realize that you need a networking plan. From the outside looking in, 100 physical servers might not seem like a big deal, but if you average a density of six virtual machines per physical server, you are actually looking at 600 virtual machines and 100 physical servers, which translates to 700 resources that require network configuration and IP addresses.

    From the networking perspective, it is important to think of virtual machines as being no different than physical servers. It is extremely important to plan out the configuration of the network and its subnetting based on the total number of virtual machines and physical servers. Otherwise, you are going to be in for a rude awakening.

  • Subnets and VLANs
    As the physical host servers and the virtual machines are scaled out, the number of subnets and VLANs will grow proportionately, so be aware that there will be an increased number of subnets and VLANs that will need to be managed.

    It is also worth noting that if you are setting up access-lists (ACLs) between VLANs (an example would be a Cisco 6509 with a multi interface Firewall Service Module or FWSM), you should be ready to manage a fairly large number of object groups and a relatively large ACL and firewall config in general.

  • ...

    Read the entire article, here.

    Published Thursday, September 28, 2006 3:23 PM by David Marshall
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