Trunks and PortChannels
Trunking, also known as VSAN trunking, is a feature specific to switches in the Cisco MDS 9000 Family. Trunking enables interconnect ports to transmit and receive frames in more than one VSAN, over the same physical link. Trunking is supported on E ports and F ports.
PortChannels aggregate multiple physical ISLs into one logical link with higher bandwidth and port resiliency for both Fibre Channel and FICON traffic. With this feature, up to 16 expansion ports (E-ports) or trunking E-ports (TE-ports) can be bundled into a PortChannel. ISL ports can reside on any switching module, and they do not need a designated master port. If a port or a switching module fails, the PortChannel continues to function properly without requiring fabric reconfiguration.
Cisco NX-OS software uses a protocol to exchange PortChannel configuration information between adjacent switches to simplify PortChannel management, including misconfiguration detection and autocreation of PortChannels among compatible ISLs. In the autoconfigure mode, ISLs with compatible parameters automatically form channel groups; no manual intervention is required.
PortChannels load balance Fibre Channel traffic using a hash of source FC-ID and destination FC-ID, and optionally the exchange ID. Load balancing using PortChannels is performed over both Fibre Channel and FCIP links. Cisco NX-OS software also can be configured to load balance across multiple same-cost FSPF routes.
Fibre Channel Port Rate Limiting
The Fibre Channel port rate-limiting feature for the Cisco MDS 9100 Series controls the amount of bandwidth available to individual Fibre Channel ports within groups of four host-optimized ports. Limiting bandwidth on one or more Fibre Channel ports allows the other ports in the group to receive a greater share of the available bandwidth under high-utilization conditions. Port rate limiting is also beneficial for throttling WAN traffic at the source to help eliminate excessive buffering in Fibre Channel and IP data network devices.
Full line-rate Fibre Channel ports provide at least 255 buffer credits standard. Adding credits lengthens distances for Fibre Channel SAN extension. Using extended credits, up to 4095 buffer credits from a pool of more than 6000 buffer credits for a module can be allocated to ports as needed to greatly extend the distance for Fibre Channel SANs.
N Port Virtualization
Cisco NX-OS software supports industry-standard N port identifier virtualization (NPIV), which allows multiple N port fabric logins concurrently on a single physical Fibre Channel link. HBAs that support NPIV can help improve SAN security by enabling zoning and port security to be configured independently for each virtual machine (OS partition) on a host. In addition to being useful for server connections, NPIV is beneficial for connectivity between core and edge SAN switches.
N port virtualizer (NPV) is a complementary feature that reduces the number of Fibre Channel domain IDs in core-edge SANs. Cisco MDS 9000 family fabric switches operating in the NPV mode do not join a fabric; they only pass traffic between core switch links and end devices, which eliminates the domain IDs for these switches. NPIV is used by edge switches in the NPV mode to log in to multiple end devices that share a link to the core switch. This feature is available only for Cisco MDS Blade Switch Series, the Cisco MDS 9124 Multilayer Fabric Switch, and the Cisco MDS 9134 Multilayer Fabric Switch.
Cisco NX-OS supports the FlexAttach feature. One of the main problems in a SAN environment is the time and effort required to install and replace servers. The process involves both SAN and server administrators, and the interaction and coordination between them can make the process time consuming. To alleviate the need for interaction between SAN and server administrators, the SAN configuration should not be changed when a new server is installed or an existing server is replaced. FlexAttach addresses these problems, reducing configuration changes and the time and coordination required by SAN and server administrators when installing and replacing servers. This feature is available only for Cisco MDS 9000 Blade Switch Series, the Cisco MDS 9124, and the Cisco MDS 9134 when NPV mode is enabled.