iSCSI (Internet Small Computer System Interface) is an IP-based (Internet Protocol) storage networking standard for linking data storage facilities. By carrying SCSI commands over IP networks, iSCSI is used to facilitate location-independent data storage and retrieval over LANs (Local Area Networks) and WANs (Wide Area Networks). iSCSI enables clients such as computers, servers, and virtual machines to use storage from your QNAP NAS as virtual disks. Clients can partition, format, and use virtual disks exactly like local disks, and then use them for storage expansion or as backup destinations.

iSCSI Target: An iSCSI storage server. In this tutorial the target is your NAS.

iSCSI initiator: An iSCSI client. Initiators connect to targets and use their storage.

Warning: Connecting more than one initiator to the same target might result in data loss or damage to the NAS disks.

Important :

An iSCSI LUN is a portion of storage space that can be utilized by initiators by connecting it to a target. In QNAP There are two types of LUNs available

Block-based LUNs use space from a storage pool. File-based LUNs use space from a volume.

Generally speaking, block-based LUNs should be used instead of file-based LUNs, as they support more snapshot and virtualization features.

A Comparison of Block-based and File-based LUN Features