ISCSI involves two main factors, 1st the ISCSI initator (client) and 2nd ISCSI target (server) which is most often a disk server running any avaiable ISCSI target daemon . ISCSI can be used to mount network drives locally and use as normal disk drives in Linux sense they can be added as /dev/sdX for e.g
Various cloud platform such as OpenStack use it to provide Elastic block storage using . The block storage service of Openstack named as Cinder. (Release Havana, Grizzly).
Further Reading: http://en.wikipedia.org/wiki/ISCSI