Cisco Cisco MDS 9000 NX-OS Software Release 4.1 Libro bianco
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N-Port Virtualization in the Data Center
What You Will Learn
N-Port virtualization is a feature that has growing importance in the data center. This document
addresses the design requirements for designing a virtual environment to support growing storage
needs. Three deployment scenarios are discussed—blade server deployments, top-of-rack fabric
designs, and VMware—along with the advantages of N-Port virtualization in these situations.
Challenges
An emerging trend in data center design is server virtualization, or the use of virtual machine
technology to prevent proliferation of physical servers. Each virtual server, to be managed as a
unique entity on the storage area network, requires a separate address on the fabric. The N-Port
virtualization feature supports this need for independent management of virtual machines and the
increased use of aggregation devices in the data center.
Introduction
With the increased use of blade center deployments and top-of-rack aggregation devices in
customer storage area network (SAN) environments, the deployment and use of aggregation
switches is becoming more widespread. Because of the nature of Fibre Channel technology,
several concerns need to be addressed when deploying large numbers of edge switches. One
major concern when designing and building Fibre Channel–based SANs is the total number of
switches or domains that can exist in a physical fabric. As the edge switch population grows, the
number of domain IDs becomes a concern. The domain is the address of a physical switch or
logical virtual fabric; the domain ID is the most significant byte in an endpoint Fibre Channel ID
(Figure 1).
Figure 1.
The switch uses this Fibre Channel ID to route frames from a given source (initiator) to any
destination (target) in a SAN fabric. This 1 byte allows up to 256 possible addresses. Some
domain addresses are used for well-known addresses, and others are reserved for future
expansion. The Fibre Channel standard allows for a total of 239 port addresses; however,
qualification of such a fabric size is nonexistent.
Another design concern is interoperability with third-party switches. In the past, different SAN
fabric vendors interpreted the Fibre Channel addressing standard differently. In addition, some
vendor-specific attributes used for switch-to-switch connectivity (or expansion port [E-Port]
connectivity) made connection of switches from different vendors challenging, leading customers
to implement edge switch technology that matched the core director type in the fabric.