Virtual I/O for storage networks


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Virtual I/O at the infrastructure level

Another area where I/O can be virtualized is in the infrastructure itself. This infrastructure virtualization could work in conjunction with virtualized network adapters or by itself. There are two types of I/O virtualization found in the infrastructure. The first is a virtualization of the switch infrastructure, basically an extension of virtual I/O at the adapter. The second is a gateway type of device that delivers broad I/O virtualization and is essentially a private I/O fabric, commonly called an I/O gateway.

Virtual I/O at the switch. Being able to control and allocate network bandwidth inside the host with virtual I/O network adapters certainly has significant value, but much of that optimization could be lost if the switch infrastructure doesn’t know how to manage it. Companies like Brocade and Cisco Systems Inc. offer switches that support virtual I/O and enable specific VMs to be guaranteed a certain level of performance throughout the rest of the network. At the switch layer, virtual machines can be identified and given certain policy settings, including those for performance characteristics. These are typically a low, medium or high quality of service, or a percentage of total bandwidth available.

But virtual I/O policy management isn’t limited to performance. Security and other settings can be configured per VM rather than per physical port. This is ideal in a virtualized server environment

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so that network settings will follow each VM when it’s migrated from one host to another.

What’s most interesting is that some vendors are working to provide a virtual I/O solution that allows for communication between the switch and the NIC so that policies set at the card level flow through the entire infrastructure between hosts and switches. Without this communication, a VM on a host that’s configured to receive 25% of the available network I/O bandwidth could lose this priority access when migrated to a secondary host. Virtual I/O at the switch layer will allow these types of configuration settings to follow the VMs as they’re moved around the environment.

Finally, some switches can even virtualize themselves. In this scenario, multiple independent switches installed in the network would appear to be one large switch. This allows for much simpler configuration and policy management because each individual switch doesn’t have to be logged into and managed. Virtualization across switches also provides greater availability management if one of the switches in the group fails.

This was first published in March 2012

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