iSCSI stands for Internet SCSI, or Internet Small Computer Systems Interface.
iSCSI is the transmission of SCSI commands and data over IP networks.
How iSCSI Works
When an application attempts to read from an iSCSI device, the SCSI read command is encapsulated inside an IP packet. The IP packet is then routed just like any other IP packet on the network. When the IP packet reaches its destination, the encapsulation is stripped off and the SCSI read command is interpreted by the iSCSI drive.
SCSI write commands are handled in the same manner.
Targets and Initiators
iSCSI uses the terms "target" and "initiator" to describe iSCSI clients and servers. In iSCSI, and "initiator" is an iSCSI client, such as a database server that accesses its data via remote storage. The storage server which provides the data would be the iSCSI "target."
Alternatives to iSCSI
The main competitor to iSCSI is FCIP (Fibre Channel over IP).
iSCSI and FCIP represent almost opposite approaches to the situation.
FCIP is an implementation of IP on Fibre Channel hardware, whereas iSCSI is an implementation of SCSI on IP hardware.
iSCSI Documentation
iSCSI is defined in RFC 3720: Internet Small Computer Systems Interface (iSCSI).
RFC 3783: Small Computer Systems Interface (SCSI) Command Ordering Considerations with iSCSI is also useful for understanding the inner workings of iSCSI technology.
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