Simplified, High-Performance 10GbE Networks Based on a Single Virtual Distributed Switch, Managed by VMware* vSphere 5.1

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3 Multiple Approaches to Virtualized

I/O Resource Sharing

The computing industry continues to develop technologies

and approaches to enhance performance, maximize server

consolidation, and work toward allowing virtualization of all

workload types. A key requirement for expanded virtualization

is the effective allocation and sharing of I/O resources; three

primary models have emerged for doing so.

• Software-based sharing typically emulates physical I/O

resources using software, translating requests so the software

representation looks to the guest as if it were the actual

physical resource. This approach requires the processor to

handle the network traffic routing and management, with the

possible result of increasing latency, reducing bandwidth, and

limiting VM performance and scalability.

• Hardware-assisted sharing allows the hypervisor to offload

part of the traffic-management function to the network

controller, reducing the burden on the virtual switch. In this

approach, VMware NetQueue*—enabled by Virtual Machine

Device Queues (VMDq), a component of Intel® Virtualization

Technology for Connectivity—can significantly enhance

the performance of the virtual switch, in terms of reducing

latency and increasing throughput. Benefits and limitations of

hardware-assisted sharing include the following:

- Benefits. Managing virtual environments with vSphere is

well supported under this model, with near-native throughput

across multiple 10GbE connections. VMDq functionality is

exposed to the VMware software using an API that gives

vSphere robust control over when to offload a specific process

to the network controller and when to handle it in software.

- Limitations. Because VMDq uses a software-based network

path through the hypervisor, it may not be appropriate for

some workloads that require particularly low latency and

high throughput, especially with small packet sizes. Examples

include databases, back-end virtual desktop infrastructure,

firewalls, and load balancers.

Physical links Physical links

Core Switch

APP

Physical

Host server

Virtual connections Virtual connections

APP

Physical

Host server

APP

Physical

Host server

VMware VDS

Figure 3. A VMware vSphere distributed switch (VDS) links virtual machine (VMs) on as many as 500 different hosts within the VMware vSphere*

environment using virtual connections.

Simplied, High-Performance 10GbE Networks Based on a Single Virtual Distributed Switch, Managed by VMware vSphere* 5.1