iSCSI

iSCSI

iscsi is a protocol that runs on top of standard TCP/IP networks. Iscsi uses the Ethernet cable to communicate to the hosts, so it is cheaper than FC protocol, because FC  cable are costlier than the Ethernet cable.

In iscsi you should be clear about the initiator and target terms, you should be knowing that what is initiator is  and what is target is.

Initiators and targets

Initiator which initiates the service or initiator which initiates the conversation between your host computer and storage device means the Ethernet port of the host is initiator and the target port is which accept the services means the storage Ethernet port are the target ports.

IQN

One more thing to understand is the iqn number each iscsi port has its own iqn number iscsi initiator service in host automatically creates iqn number and iscsi target in storage has its own iqn number , so if you change the hostname of the storage may be the iqn number of that storage will get change. The conclusion is that the iscsi ports have their own iqn number and they are unique.

DataDomain or Domain

In a basic iSCSI SAN, a storage array advertises its SCSI LUNs to the net-work (the targets), and clients run an iSCSI driver (the initiators) that looks for those LUNs. In a larger setup with, say, fifty or more clients or storage devices or both, you probably don’t want every client to see every storage device. It makes sense to block off what each host can see and which storage devices they have the potential of using. This is accomplished by registering the names of the initiators and targets in a central location, and then pairing them into groups. A logical grouping, called a data domain, partitions the registered initiators and targets into more manageable group.