SCST is designed to provide unified, consistent interface between SCSI
target drivers and Linux kernel and simplify target drivers development
as much as possible. Detail description of SCST's features and internals
could be found on its Internet page http://scst.sourceforge.net.
SCST supports the following I/O modes:
 * Pass-through mode with one to many relationship, i.e. when multiple
   initiators can connect to the exported pass-through devices, for
   the following SCSI devices types: disks (type 0), tapes (type 1),
   processors (type 3), CDROMs (type 5), MO disks (type 7), medium
   changers (type 8) and RAID controllers (type 0xC).
 * FILEIO mode, which allows to use files on file systems or block
   devices as virtual remotely available SCSI disks or CDROMs with
   benefits of the Linux page cache.
 * BLOCKIO mode, which performs direct block IO with a block device,
   bypassing page-cache for all operations. This mode works ideally with
   high-end storage HBAs and for applications that either do not need
   caching between application and disk or need the large block
   throughput.
 * User space mode using scst_user device handler, which allows to
   implement in the user space high performance virtual SCSI
   devices. Comparing with fully in-kernel dev handlers this mode has
   very low overhead (few %%)
 * "Performance" device handlers, which provide in pseudo pass-through
   mode a way for direct performance measurements without overhead of
   actual data transferring from/to underlying SCSI device.
In addition, SCST supports advanced per-initiator access and devices
visibility management, so different initiators could see different set
of devices with different access permissions. See below for details.
Full list of SCST features and comparison with other Linux targets you
can find on http://scst.sourceforge.net/comparison.html.