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Top five VMware network performance tips

Tweaking a few, simple configuration settings can improve VMware network performance and ensure that VMs receive their fair share of bandwidth.

The more virtual machines you're running on a VMware vSphere infrastructure, the more important it is to optimize...

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Let’s take a look at five of the most popular strategies for improving VMware network performance without spending a lot of money.

Network performance tip No. 1: Use traffic shaping on the virtual switch
By default, a virtual machine (VM) can use all bandwidth on a network interface. Without limits, a few VMs can use all the available bandwidth, which will hurt the performance of other VMs.

If this is the case in your network, traffic shaping may be a good solution to improve VMware network performance. This option allows you to specify average bandwidth, peak bandwidth and burst size to make sure all VMs get their share of the available bandwidth. You'll find this option under the virtual switch properties, and you can apply it to any of the VMs that are connected to that switch.

Network performance tip No. 2: Separate VM traffic from management traffic
By default, your ESXi server has one network interface, which connects the VMs to the network. But you'll also use it to manage these VMs. That means, you may have problems managing the VMs and the ESXi hosts if the network is too busy.

You can configure a dedicated management network to avoid these issues and improve VMware network performance. From the Configuration pane, choose Networking > Add Networking. From here, you can choose between two network types. Use the Virtual Machine network type for VM-generated traffic, and use the VMkernel network type for vSphere-related traffic, including bandwidth-heavy services, such as vMotion or iSCSI network traffic.

Network performance tip No. 3: Configure the management network for redundancy
The management network encompasses much more than just the management traffic for VMs. It's also used for bandwidth-intense operations. You don't want these kinds of operations to stop if a network interface card (NIC) fails. Therefore, make sure that you've set up the management network for redundancy by using two, dedicated network cards.

To do this, select the Networking option from the Configuration tab and click the management vSwitch properties. You can now select an additional physical network card to connect to the vSwitch.

Network performance tip No. 4: Restore default network settings
Hopefully, your configuration changes will improve VMware network performance. However, networking is complicated, and if a change to the complex topology leads to a decrease in performance, it can be difficult to revert to the original configuration.

There is an easy way out, though. On the ESXi host console, you'll find an option to restore the default VMware network settings. This selection removes all of your network configuration changes and lets you start all over again. Make sure that you really want to restore the defaults, because all current connections are dropped, and it will take some time to get your virtual network up and running again.

Network performance tip No. 5: Using PCI pass-through for high-demand VMs
Some VMs need so much bandwidth that they may be better off on their own dedicated server. Fortunately, for this kind of high-demand VM, another solution, called PCI pass-through, can improve VMware network performance. This approach allows a VM to access a physical NIC directly, bypassing the hypervisor. Using this setup, you'll dedicate a network board to one VM.

To configure PCI pass-through, select Configure Pass-through from the Configuration tab. Next, select the network card that you want to assign as a pass-through card. You can now assign the network card to a VM, but you will first have to restart the VM host.

These tips are just a few of the many options that can optimize VMware network performance. As organizations increase their consolidation ratios, paying close attention to simple network settings can dramatically improve performance and curtail the need for an expensive upgrade.

This was last published in March 2012

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