HP StorageWorks 16-EL HP StorageWorks Zoning V3.1.x/4.1.x User Guide (AA-RS26C - Page 54

Storage Area Networks

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Zoning Concepts and Guidelines 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. 54 Zoning Version 3.1.x/4.1.x User Guide

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Zoning Concepts and Guidelines
54
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.