The purpose of iSCSI is simple: make a block storage device, such as a disk or a volume, accessible over a mainstream IP network. When iSCSI was introduced it looked like a nice niche market because 1Gbps Ethernet had become the standard baseline for network throughput across the board but now 10Gbps Ethernet is a reality. With this faster and wider bandwidth iSCSI and iSCSI targets have been elevated from a niche tool to be the conventional solution. The immediate benefit of iSCSI is clear: no-cost/low-cost storage networking. The long term advantage of iSCSI is the flexibility it provides as a product of the cost, systems that you would never have imagined putting a Fibre Channel HBA in are now prime candidates for iSCSI and iSCSI target.
Most industry focus has been placed on creating iSCSI target disks though iSCSI tape and medium changer targets are popular as well. So far, physical devices have not featured native iSCSI interfaces on a component level. Instead, devices with SCSI Parallel Interface or Fibre Channel interfaces are bridged by using iSCSI target software, external bridges, or controllers internal to the device enclosure.
Alternatively, disk and tape targets can be virtualizations. Rather than representing an actual physical device, an emulated virtual device is presented. The underlying implementation can deviate drastically from the presented target as is done with Virtual Tape Library (VTL) solutions. VTLs use disk storage for storing data written to virtual tapes. As with actual physical devices, virtual targets are presented by using iSCSI target.
software, external bridges, or controllers internal to the device enclosure.
All storage protocols, FC, pSCSI, iSCSI have two “ends” in the connection. These ends are the Initiator and the Target. In iSCSI we call them iSCSI Initiator and iSCSI target. The iSCSI Initiator: Requests, or initiates, any iSCSI communications. It requests all SCSI operations like read or write. An initiator is usually located on the host/server side (either an iSCSI HBA or iSCSI SW initiator) iSCSI target.
: The iSCSI target is the storage device itself or an appliance that controls and serves volumes or virtual volumes. The target is the device that performs the SCSI command or bridges it to an attached storage device. iSCSI targets, like the iSCSI V-Switch, can be disks, tapes, RAID arrays, tape libraries, FC Fabrics, etc.
For more about iSCSI and iSCSI please visit SANRAD and check out their FAQ section at Sanrad