iSCSI stands for "Internet SCSI" and is a standard that allows for using the SCSI protocol over Internet (TCP/IP) connections. Especially with the advent of Gigabit Ethernet, it has become affordable to attach iSCSI storage servers simply as remote hard disks to a computer network. In iSCSI terminology, the server providing storage resources is called an "iSCSI target", while the client connecting to the server and accessing its resources is called "iSCSI initiator".
VirtualBox can transparently present iSCSI remote storage to a virtual machine as a virtual hard disk. The guest operating system will not see any difference between a virtual disk image (VDI file) and an iSCSI target. To achieve this, VirtualBox has an integrated iSCSI initiator.
VirtualBox's iSCSI support has been developed according to the iSCSI standard and should work with all standard-conforming iSCSI targets. To use an iSCSI target with VirtualBox, you must use the command line; see Section 8.18, “VBoxManage storageattach”.