In modern data center or enterprise environment, an iSCSI target often resides in a large storage array. These arrays can be in the form of commodity hardware with free-software-based iSCSI implementations, or as commercial products such as in StorTrends, Pure Storage, HP StorageWorks, EqualLogic, Tegile Systems, Nimble storage, Reduxio, IBM Storwize family, Isilon, NetApp filer, EMC Corporation NS-series, CX4, VNX, VNXe, VMAX, Hitachi Data Systems HNAS, or Pivot3 vSTAC.
Nearly all modern mainstream server operating systems (such as BSD, Linux, Solaris or Windows Server) can provide iSCSI target functionality, either as a built-in feature or with supplemental software. Some specific-purpose operating systems (such as FreeNAS, NAS4Free, Openfiler, OpenMediaVault, or based on OpenSolaris and derivatives like napp-it, NexentaStor, OmniOS and OpenIndiana) implement iSCSI target support.
In SCSI terminology, LUN stands for logical unit number. A LUN represents an individually addressable (logical) SCSI device that is part of a physical SCSI device (target). In an iSCSI environment, LUNs are essentially numbered disk drives. An initiator negotiates with a target to establish connectivity to a LUN; the result is an iSCSI connection that emulates a connection to a SCSI hard disk. Initiators treat iSCSI LUNs the same way as they would a raw SCSI or IDE hard drive; for instance, rather than mounting remote directories as would be done in NFS or CIFS environments, iSCSI systems format and directly manage filesystems on iSCSI LUNs.
In enterprise deployments, LUNs usually represent subsets of large RAID disk arrays, often allocated one per client. iSCSI imposes no rules or restrictions on multiple computers sharing individual LUNs; it leaves shared access to a single underlying filesystem as a task for the operating system.