12.0 Mass Storage over IP Networks—iSCSI

One of the central tasks in computer centers and when operating servers is providing hard disk capacity for server systems. Fiber channel is often used for this purpose in the mainframe sector. So far, UNIX computers and the majority of servers are not connected to central storage solutions.

linux-iSCSI provides an easy and reasonably inexpensive solution for connecting Linux computers to central storage systems. In principle, iSCSI represents a transfer of SCSI commands on the IP level. If a program starts an inquiry for such a device, the operating system produces the necessary SCSI commands. These are then embedded in IP packages and encrypted as necessary by software that is commonly known as an iSCSI initiator. The packages are then transferred to the corresponding iSCSI remote station, also called iSCSI target.

Many storage solutions provide access over iSCSI, but it is also possible to run a Linux server that provides an iSCSI target. In this case, it is important to set up the Linux server optimized for file system services. The iSCSI target just accesses block devices in Linux. Therefore it is possible to use RAID solutions to increase disk space as well as a lot of memory to improve data caching. For more information about RAID, also see Section 7.2, Soft RAID Configuration.