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 .

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 .