Storage area networks – HP StorageWorks MSA 2.8 SAN Switch User Manual
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Zoning Concepts and Guidelines
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Zoning Version 3.1.x/4.1.x User Guide
Storage Area Networks
The storage area network brings the connectivity of networks to the SCSI
protocol. The Fibre Channel standard provides for up to 16 million devices
attached to the network. This change in scale required a new method to discover
the devices on the fabric, so that discovery can be accomplished in an acceptable
time frame.
The fabric well-known service “nameserver” was implemented to address this
need. When a device initially accesses the fabric, it must perform a login process.
During this process the device will register with the nameserver. The nameserver
records information about the device; that is, protocols supported, World Wide
Name (WWN), network address, supported class of service, for example.
When an initiator accesses the network it can query the nameserver for all
attached devices and their capabilities. Any initiator can query (probe) the fabric
for all targets, and then proceed to initialize the targets and perform I/O. This can
be disastrous if another initiator is already utilizing the target and has stored data
on it such as with a disk or tape. The process of zoning is utilized to provide a
virtual SCSI bus that limits the devices that an initiator can discover and access.