Blue Gears – Combining Networks on VMware Virtual Switches

An often discussed VMware ESX issue is how to combine the various networks within the virtual infrastructure or even if they should be combined on the same vSwitch. Combining networks should only be done if you are low on network ports. The common rule is to have at least 2 physical NICs per network and that these NICs need to connected to difference physical switches. Yet, they are connected to the same virtual switch. However, if you have for example the following networks, then you could need a huge number of physical NICs which is not always possible, so we need to combine networks. * Administrative Network (Service Console or SC) * VMotion Network * Storage Network * Production Network * DMZ Network These would require minimally 10 pNICs if we go by the basic rule. However, this is not always possible, so what is safe to combine to reduce the over all pNIC requirements? Many people combine SC and VMotion onto the same pair of pNICs while keeping all the other networks unshared. This reduces the pNIC requirement by two. Which is still not always enough. The other combination that is prevalent is to combine SC, VMotion, and Storage onto the same pair of pNICs. This reduces the total pNICs by two more pNICs. Lastly another combination is to combine Production and DMZ networks on the same pNICs with yet another 2 pNIC reduction. There are trade-offs with these combinations, the first could be considered security, but this depends on how much trust you put in VLANs. If you are instead using subnets, then these combinations due cause security issues, specifically the DMZ mixed with the production network. The DMZ network should be 100% segregated from any other network. At the very least there will be data comingling on the wire. The other is performance as combining storage networks on other highly used networks will affect overall virtualization performance. VMotion and SC can be heavily used at specific times and these will adversely affect storage network performance and visa versa. The last trade off deals with redundancy. You really want as much network redundancy as possible, and when you combine networks on the same pNICs you loose quite a bit of individual network redundancy. The use of VLANs and subnets will help with the redundancy issue. If you have to combine networks stick with just combining the SC and VMotion networks. Once you add in more combinations the trade-offs become very important considerations.