Because IP packets are used, data can be moved using standard network wiring and routing. Adding or moving storage is -- conceptually at least -- merely a matter of plugging or unplugging a storage unit on the network. While the intent is to use it primarily with physically nearby units, there is no limitation other than speed of transfer that prevents iSCSI from being used with storage devices at remote locations..
iSCSI places communication modules between an operating system and network and between the storage device an network. These handle packet creation, assembly, transmission, and optionally encryption/decryption. Unlike NICs, there is minimal CPU loading because protocol drivers operate in the Host Adapter firmware rather than the server CPU. Encryption (IPsec) is an issue because there are problems interfacing it with hardware compression techniques used to speed up data transfers.
iSCSI data rates are limited primarily by the transport medium.
An iSCSI Version 1.0 standard has been agreed to and is in the approval process as of September 2008. Several companies are working on iSCSI devices compliant with the 1,0 standard. Companies including IBM and Cisco have shipped iSCSI devices already. It is unclear if they comply with the iSCSI 1.0 spec.
Return To Index Copyright 1994-2008 by Donald Kenney.