HP StorageWorks 2/16V HP StorageWorks Fabric OS 5.X Procedures User Guide (AA- - Page 179

Table 34 Approaches to fabric-based zoning Form Single HBA Application Operating system Port allocation No fabric zoning Description Zoning by single HBA most closely re-creates the original SCSI bus. Each zone created has only one HBA (initiator) in the zone; each of the target devices is added to the zone. Typically, a zone is created for the HBA and the disk storage ports are added. If the HBA also accesses tape devices, a second zone is created with the HBA and associated tape devices in it. In the case of clustered systems, it could be appropriate to have an HBA from each of the cluster members included in the zone; this is equivalent to having a shared SCSI bus between the cluster members and presumes that the clustering software can manage access to the shared devices. In a large fabric, zoning by single HBA requires the creation of possibly hundreds of zones; however, each zone contains only a few members. Zone changes affect the smallest possible number of devices, minimizing the impact of an incorrect zone change. This zoning philosophy is the preferred method. Zoning by application typically requires zoning multiple, perhaps incompatible, operating systems into the same zones. This method of zoning creates the possibility that a minor server in the application suite could disrupt a major server (such as a web server) disrupting a data warehouse server. Zoning by application can also result in a zone with a large number of members, providing greater susceptibility to administrative errors, such as RSCNs going out to a larger group than necessary. Zoning by operating system has issues similar to zoning by application. In a large site, this type of zone can become very large and complex. When zone changes are made, they typically involve applications rather than a particular server type. If members of different operating system clusters can see storage assigned to another cluster, they might attempt to own the other cluster's storage and compromise the stability of the clusters. Avoid zoning by port allocation unless the administration team has very rigidly enforced processes for port and device allocation in the fabric. It does, however, provide some positive features. For instance, when a storage port, server HBA, or tape drive is replaced, the change of WWN for the new device is of no consequence. As long as the new device is connected to the original port, it continues to have the same access rights. The ports on the edge switches can be pre-associated to storage ports, and control of the fan-in ratio (the ratio of the input port to output port) can be established. With this pre-assigning technique, the administrative team cannot overload any one storage port by associating too many servers with it. Using no fabric zoning is the least desirable zoning option because it allows devices to have unrestricted access on the fabric. Additionally, any device attached to the fabric, intentionally or maliciously, likewise has unrestricted access to the fabric. This form of zoning should be used only in a small and tightly controlled environment, such as when host-based zoning or LUN masking is deployed. Zone objects A zone object is any device in a zone, such as the: • Physical port number or area ID on the switch • Node WWN (N-WWN) • Port WWN (P-WWN) Zone objects identified by port number or area number are specified as a pair of decimal numbers in the form d, area (d is the domain ID of the switch and area is the area number on that switch). For example, on Core Switch 2/64 or SAN Director 2/128, 4,46 specifies port 14 in slot number 3 (domain ID 4, area 46). On fixed-port models, 3,13 specifies port 13 in switch domain ID 3. When the physical port number specifies a zone object, all devices connected to that port are in the zone. If the physical port is an arbitrated loop, all devices on the loop are part of the zone. Fabric OS 5.x administrator guide 179