11.0 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 6.2,
Soft RAID Configuration.