Three major ways to increase network available bandwidth for virtual machines

The general trend of server virtualization is moving toward increasing the density of virtual machines (VMs) within the host server. As the density of VMs increases, the hardware cost per VM gradually decreases. Network administrators usually configure the server with as much CPU and memory as possible, but the server's network port limits the number of VMs that can be hosted because each VM requires a network port to communicate with the outside world. Typically, multiple VMs share a single Network ports, bandwidth is also shared, so the problem comes. If you encounter a VM running a network-intensive application, the situation will become very bad, the network bandwidth is not enough, and the network congestion exists in the virtual world.

The good news is that the available bandwidth available to the VM can be increased by some means, which makes the increase of VM density a reality.

Adding a network port

The easiest way is to install a network card on the server. In general, the server only integrates one or two integrated network card interfaces on the motherboard when it leaves the factory. Expansion slot, we can increase the number of network ports through the expansion slot, but it should be noted that you should try to choose a multi-port network card, such as some PCI-X and PCI Express network cards with 4 independent ports.

Another way is to use an external network card, such as a USB network card. But for the server, we do not recommend the use of USB NIC, especially some virtualization platforms do not support the exposure of USB devices to the VM, even so, sometimes can come in handy.

Regardless of how the network port is allocated, it is best to reserve a port for management communication. You cannot assign all network ports to the VM. A management channel must be set between the VM and the host server. If you are virtualizing The software supports exposing the USB NIC to the VM. You can reserve a USB NIC for communication between the VM and the host server.

Although it is possible to share a network card between multiple VMs, the problem is that the bandwidth provided by a single network card is limited, and all VMs bound to the network card share the bandwidth. If possible, you should use a faster NIC as much as possible, such as a 10Gb Ethernet card, and a few Gigabit NICs.

Using Virtual Networks

If you can't add physical NICs, there is another way to minimize the VM's need for network bandwidth.

One way to achieve this goal is to create a virtual network that exists entirely inside the host server. If you use Microsoft Hyper-V or VMware, at least one virtual network is created by default, and each VM is used. The physical NIC is connected to the virtual switch, and the virtual switch is connected in sequence to the virtual NIC of each VM.

The virtual network provides the VM with a connection to the physical network, but it cannot access the physical network, so that we can use the virtual network to offload some of the communication that originally used the physical network, thus reducing the physical network bandwidth requirements.

For example, suppose you have a virtualized web server, the back-end SQL Server database runs on another virtual machine, creating a virtual network between the web server and the database server, so that the database query will not The physical network port indirectly increases the available bandwidth of the VM.

Assigning network ports according to VM needs

Creating a virtual network can transfer a large amount of network traffic to a virtual network. If this is not possible, there is a last resort, according to the VM's network requirements. Assign a network port. Of course, you can do this when you create a virtual network.

Not every VM has the same network bandwidth requirements. It is not realistic to assign a network port to each VM. Therefore, analyze the network requirements of each VM and properly share the VM ports with low bandwidth requirements. It is ideal to specify a dedicated port for VMs with high bandwidth requirements. For example, suppose you have a SQL Server server, you should assign it an exclusive network port. Instead, for domain controllers and DHCP servers, they need less bandwidth and can share a single port.

In short, the available bandwidth of the network limits the density of VMs on the host server, but there are many ways to increase the network bandwidth allocated to the VM. We will see more and more on the way to maximize VM density. More solutions have emerged.
Author: Brien M. Posey Translator: Huang Yongbing