Specifications
DATA CENTER BEST PRACTICES
SAN Design and Best Practices 57 of 84
much smaller number (56 is recommended in Brocade fabrics). The domain count limit typically comes into play
when a large number of small-port-count switches are deployed. Large-bladed server deployments, for example,
can easily push the domain count up over recommended limits when embedded blade switches are part of the
implementation. FC switches in blade server enclosures typically represent fewer than 32 ports.
NPIV was originally developed to provide access to Fibre Channel devices from IBM mainframes and to improve
the efciency of mainframe I/O for virtualized environments. NPIV is part of the Fibre Channel standard and has
been put to use in many open systems storage deployments. Brocade switches and directors as well as the
Brocade Access Gateway support NPIV.
NPIV allows for many ows (connections) to share a single physical link. Figure 39 illustrates a single platform
that supports ows from separate VMs through a single upstream link to a fabric via a shared HBA.
fig36_SAN_Design
Single Physical Hypervisor Platform
VMVM VM
NPIV connections
Single
physical
link
VM
Shared HBA
Access Gateway with NPIV support
VM VM
Brocade backbone,
director, or switch
Figure 39. VMs supported on a single link to a fabric via NPIV.
A device or switch connecting to another switch via an NPIV-enabled port does not require a domain ID, does
not do any zoning, and behaves much more like an end device (or group of devices) than a switch. The Brocade
Access Gateway was originally designed to reduce domain ID proliferation with the introduction of embedded
blade switches, which use low-port-count switches that reside in blade server chassis. In most environments,
these embedded switches are deployed in large quantities, which not only lead to high-domain-count fabrics,
but also increases switch administration overhead. The Brocade Access Gateway eliminates or reduces both of
these issues and is supported on all Brocade embedded switches and some xed-port switch platforms. The
Brocade Access Gateway connects initiators such as host HBAs on its “downstream” F_Ports to one or more
fabrics via “upstream” N_Ports.
Benefits of the Brocade Access Gateway
•Scalability: You can add many Access Gateways to a fabric without increasing the domain count. A major
scalability constraint is avoided when small-port-count switches or embedded switches are part of an
infrastructure. Registered State Change Notications (RSCNs) are also greatly reduced—only those that are
related to the initiators on the downstream Access Gateway ports are passed on through to the fabric. Since
it is essentially a device, the Access Gateway can connect to more than one fabric from its upstream ports.
Brocade Access Gateways can be cascaded to reduce the number of fabric connections required to support a
given workload or trafc level from the attached hosts.