In a conventional network, hosts are assumed to be intelligent and network is to facilitate the communication betweeh nodes and ensure data delivery. In SAN, am emd devoce is relative dumb such as a JBOD. Targets are passive, listening for requests and do not advertise itself. The SAN must provide a discovery service, which is a function of the simple name server (SNS) implemented in switch and director.
SAN is a self-configuring network. Switches automatically negotiate with the rest of the fabric for address allocation. A device connecting to the fabric perform a logon to obtain a unique 3-byte address. The device then register with SNS to inform it of its capabilities. Host can query SNS for accessible targets.
Support services such as LUN masking, zoning and stat change notification provide control over the fabric. Zoning places authorized storage devices and serves into a common communication domain. Devices outside the zone cannot access those inside the zone. Zoning manipulate the fabric's response to SNS queries by servers so that only authorized devices are returned.
Registered state change notification (RSCN) is a mean to alert entry or disappearance of stirage asets on the fabric. Upon alert, hosts can query SNS for additional devices.
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