I had a discussion with one of my readers last week and just read this post on the VMTN community which triggered this article.
When you create a highly available environment take into account that you will need to have enough vSwitch ports available when a failover needs to occur. By default a vSwitch will be created with 56 ports and in general this is sufficient for most environments. However when two of your hosts fail in a 10 host cluster you might end up with 60 or more VMs running on a single host. If this would happen several VMs would not have a vSwitch port assigned.
The most commonly used command when creating an automated build procedure probably is:
esxcfg-vswitch -a vSwitch1
This would result in a vSwitch named “vSwitch1” with the default amount of 56 ports. Now it is just as easy to set it up with 128 ports for instance:
esxcfg-vswitch -a vSwitch1:128
Always design for a worst case scenario. Also be aware of the overhead, some ports are reserved for internal usage. You might want to factor in some additional ports for this reason as for instance in the example above you will have 120 ports available for your VMs and not the 128 you specified.