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Hubs based on private, arbitrated loops were used to build early SANs. Although these early SANs had a theoretical maximum of 126 devices, the realistic maximum was much lower. Additionally, with many devices sharing a loop, performance often varied and troubleshooting was difficult at best.
With the introduction of the fully public switch, SAN fabrics can theoretically contain over 7.7 million nodes, and thanks to newer switch features -- particularly zoning -- creating and managing these large SANs is now easier than ever before. Best of all, full fabric-based switches allow storage managers to maximize the effectiveness of currently installed private loop devices.
SAN Switch Zoning
In order to allocate appropriate storage where it makes the most sense, switch zoning allows the SAN manager to partition the SAN into various groupings. A typical SAN switch (1Gb switch) normally supports four zone types:
- Hard zones
- Name server zones
- Broadcast zones
- Segmented loop zones
The preceding zone types give the SAN manager the flexibility to partition the SAN into logical groupings of devices that can share information. The information can be shared whether these devices use private or public fabric addressing schemes, thus maximizing the investment in the installed private loop devices.
Defining zones, or adding or changing devices within a zone of a SAN switch, is easily performed via SAN management software. The SAN manager can dynamically reconfigure the current fabric zone configuration to add or reallocate devices to existing or new zones to meet the growth needs of the company. All of this is accomplished by using a SAN Graphical User Interface (GUI).
Zoning can also be used to simplify a heterogeneous environment within the same switch fabric. By keeping these devices separated by zones to prevent conflicts between fabric devices, the SAN manager has the freedom to add any type of device to the fabric.