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The goal of this document is to help administrators optimize network I/O performance both in standalone Cisco Unified Computing System™ (Cisco UCS®) servers and in configurations operating under Cisco UCS Manager. Note that although this document covers I/O performance optimization for the Cisco UCS virtual interface card (VIC), factors such as CPU, BIOS, memory, operating system, and kernel can contribute to overall I/O workload performance. For more specific performance optimization recommendations, please refer to Cisco® BIOS best practices tuning guides and Cisco Validated Designs for specific workloads.

The Cisco UCS virtual interface card, or VIC, is a converged network adapter (CNA) designed for Cisco UCS blade and rack servers. The Cisco VIC is a stateless hardware device that is software programmable, providing management, data, and storage connectivity for Cisco UCS servers. Installed as a part of Cisco UCS or a standalone environment, the VIC is used to create PCI Express (PCIe) standards-compliant virtual interfaces: both virtual network interfaces (vNICs) and virtual host bus adapters (vHBAs). Indistinguishable from hardware NICs and HBAs, these interfaces can be dynamically defined and configured at the time of server provisioning.

Unless otherwise noted, this document is applicable to all past and present Cisco UCS VICs—for both blade and rack server platforms—operating under either Cisco UCS Manager or Cisco Integrated Management Controller (IMC).

The target audiences for this document are systems architects, system and server administrators, and any other technical staff who are responsible for managing Cisco UCS servers. Although this document is intended to appeal to the widest possible audience, the document assumes that the reader has an understanding of Cisco UCS hardware, terminology, and configuration.

The sections that follow describe the Cisco UCS VICs, vNICs, and the capabilities of various configurations.

The Cisco UCS VIC is available in a variety of models and form factors, allowing it to be supported in both Cisco UCS blade and rack servers (Figure 1). Depending on the generation and model, the adapter includes a PCIe 2.0 or 3.0 interface with either x8 or x16 connectivity and 10-, 20-, 25-, 40-, 50-, and 100-Gbps port speeds. For more specific information about capabilities, speed, operation, and server and network connectivity, refer to the data sheets for individual Cisco UCS VIC and server models.

Through unique Cisco® technology and policies, each Cisco UCS VIC provides up to 256 PCIe interfaces (the number depends on the Cisco UCS VIC model). Each virtual interface (vNIC or vHBA) created on the Cisco VIC application-specific integrated circuit (ASIC) is presented to the operating system as a fully standards-compliant PCIe bridge and endpoints. Each vNIC gets its own PCI address, memory space, interrupts, and so forth. The vNIC does not require any special driver and is supported as a part of the standard OS installation package.

Figure 2 provides a logical view of the Cisco UCS VIC, including its dual connections to a redundant pair of Cisco UCS fabric interconnects or LANs. The kernel’s standard Ethernet NIC (eNIC) driver allows the OS to recognize the vNICS. Having the most current eNIC driver can help improve network I/O performance, and Cisco recommends that the driver be updated based on the Cisco UCS Manager or Cisco IMC firmware and OS version level. The recommended driver level can be found through the Cisco UCS Hardware and Software Interoperability Matrix Tool (see the link at the end of this document).

By default, two vNICs are created on each Cisco UCS VIC, with one bound to each of the adapter’s interfaces (ports 0 and 1). The server administrator can create additional vNICs to help segregate the different types of traffic that will be flowing through the adapter. For example, as shown in Figure 3, a server administrator might create four vNICs as follows:

●Two vNICs for management (one for side-A connectivity and one for side-B connectivity)

●Two additional vNICs for data (one for side-A connectivity and one for side-B connectivity)

**Figure 3.**Four vNICs are created for redundant data and management connections to Cisco UCS fabric interconnects or LANs

The total number of supported vNICs is OS specific, and each OS allocates a different number of interrupts to the adapters. For the exact number of supported vNICs, refer to the Configuration Limit Guide on Cisco.com (see the link at the end of this document).

The 1200, 1300 and 1400 series Cisco UCS rack server VICs have two external ports, except for the 4th-generation Cisco UCS VICs 1455 1457, and 1467, which have four external adapter interfaces. On the Cisco UCS VIC 1455, 1457 and 1467, ports (1,2), and ports (3,4), are hardware port-channeled by default. This hardware port-channel is internal to the VIC 1455, 1457, and 1467 hardware. The hardware port-channel cannot be disabled in Cisco UCS Manager mode but when servers are in standalone mode the VIC hardware port-channel can be disabled from the Cisco IMC.

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