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LIO Target
RisingTide Systems
Multiprotocol Target Engine
Original author(s) Nicholas Bellinger
Developer(s) RisingTide Systems LLC
Initial release January 14, 2011 (2011-01-14)
Stable release 4.1.0 / June 20, 2012;
9 years ago
Preview release 4.2.0-rc5 / June 28, 2012;
9 years ago
Development status Production
Written in C
Operating system Linux
Type Target engine
License GNU General Public License
LIO architecture overview.
LIO iSCSI architecture diagram.
SCSI standards diagram.
TCM_QLA2xxx running at line rate HW target mode from with PCIe device passthrough with MSI-X polled interrupts across Linux/SCSI qla2xxx LLD request and response rings
TCM v4.0 QLAXXX prototype using PCIe device passthrough for target mode MSI-X interrupts, and QEMU Megasas HBA emulation into Windows7 64-bit guest.
FILEIO with a Tcm_loop SCSI port on KVM x86_64 host running v2.6.36-rc3+ with QEMU lsi53c895a HBA emulation into an OS/2 Warp v4 guest. A HPFS partition has been formatted and mounted as DRIVE D:

The Target (target_core_mod.ko) is the generic multiprotocol target engine of LIO. It is the standard Linux multiprotocol target engine with v2.6.38 (spring 2010 release).[1][2][3]

LIO Target supports a wide range of platforms (from PC architecture to mobile devices, STBs and game consoles), based on a wide range of CPU architectures (x86, ia64, Alpha, Cell, PPC, ARM, MIPS, etc.), basically all existing Linux block devices for backstores, and a growing number of fabric modules.

The LIO SCSI engine implements a significant SPC-3/SPC-4 feature set with support for high-end SCSI features in a fabric agnostic way, such as Persistent Reservations (PR), Asymmetric Logical Unit Assignment (ALUA), Multiple Connections per Session (MC/S) and ERL=2.



A backstore subsystem plugin is a physical storage object that provides the actual storage underlying an SCSI Endpoint. Backstore objects can be added via the Storage Hardware Abstraction Layer (SHAL) that brings storage hardware into the Target engine as raw block devices, on which the full Linux stack just works (including complex functionality such as software RAID, the LVM, snapshots, virtualization, etc.).

The Target supports the SCSI-3 standard for all backstore devices (block devices and/or VFS):

The SCSI functionality is implemented directly in the target engine in a fabric agnostic way, including a number of high-end features, such as Persistent Reservations (PRs) and Asymmetric Logical Unit Assignment (ALUA), which have been available with LIO 3, following the SPC-4 standard.

Fabric modules

The LIO Fabric Hardware Abstraction Layer (FHAL) allows all protocol-specific processing to be encapsulated in fabric modules, and thus can also accommodate novel fabric technologies and requirements:


The LIO 3 CLI manual describes a simple userspace shell (lio-utils) for LIO 3 (Target+iSCSI). It also describes how to setup a number of different subsystem storage object backstores for LIO LUN endpoints:

RisingTide Systems makes available upon request and for free RTSadmin, a comprehensive, powerful, yet easy storage management tool that can efficiently handle even complex LIO installations.

Lastly, the Target engine configuration is mapped into Target/configFS, where it can be configured manually from user space by using inter- and intra-module symbolic links.


The following specifications are available as T10 Working Drafts:




Timeline of the LinuxIO
Release Details 2011 2012 2013 2014 2015
123456789101112 123456789101112 123456789101112 123456789101112 123456789101112
4.x Version 4.0 4.1
Feature LIO Core Loop back FCoE iSCSI Perf SRP
vHost Perf Misc 16 GFC iSER Misc VAAI Misc DIF Core
DIF iSER DIF FC vhost TCMU Xen Misc Misc virtio 1.0 Misc NVMe OF
Linux 2.6.38 2.6.39 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 3.20 3.21 3.22

See also


  1. Linus Torvalds (1/14/2011). "Trivial merge". torvalds/2.6.git. 
  2. James Bottomley (12/21/2010). "[SCSI] target: Add LIO target core v4.0.0-rc6". scsi-misc-2.6.git. 
  3. Jonathan Corbet (12/22/2010). "Shooting at SCSI targets". 

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