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LIO Target
RTS OS 2.0 120207a.png
LIO Unified Target
Original author(s) Nicholas Bellinger
Developer(s) Datera, Inc.
Initial release January 14, 2011 (2011-01-14)
Stable release 4.1.0 / June 20, 2012;
21 months ago
Preview release 4.2.0-rc5 / June 28, 2012;
21 months 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 Portal Group and multipath architecture overview.
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 engine of LIO Unified Target, which has become the new Linux standard with kernel version 2.6.38.[1][2] LIO Unified 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.), a growing number of fabric modules, and basically all existing Linux block devices for backstores.

The LIO SCSI engine implements a comprehensive SPC-3/SPC-4 feature set with support for high-end SCSI features in a fabric-agnostic way, such as Persistent Reservations (PR) and Asymmetric Logical Unit Assignment (ALUA) as being used by VMware ESX 4 and vSphere 4.

The LIO Target engine went upstream into the Linux 2.6.38 kernel on 1/14/2011.[3]



targetcli (from Datera, Inc.) is a comprehensive, powerful, yet easy storage management tool that can efficiently handle complex LIO Target installations.


The rollout of the target engine and fabric modules into the Linux mainline kernel is unfolding as follows:

Fabric modules

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


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 (S-HAL) 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.


The following specifications are available as T10 Working Drafts:




Timeline of the Linux-IO Target
Release Details 2010 2011 2012 2013 2014
123456789101112 123456789101112 123456789101112 123456789101112 123456789101112
4.x Version 4.0
Feature Target Core Loop back FCoE iSCSI Perf SRP
vHost Perf Misc 16 GFC iSER Misc VAAI Misc DIF
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.x Version 3.2 3.4 3.5
Feature Misc Open-FCoE Backports

See also


  1. Thorsten Leemhuis (3/2/2011). "Kernel Log: Coming in 2.6.38 (Part 4) - Storage". Heise Online. 
  2. Jonathan Corbet (12/22/2010). "Shooting at SCSI targets". 
  3. Nic Bellinger (1/24/2011). "[ANNOUNCE]: TCM/LIO v4.0.0-rc7 for 2.6.38-rc2". 
  4. Linus Torvalds (3/14/2011). "Linux 2.6.38". 
  5. Linus Torvalds (1/14/2011). "Target merge". 
  6. Linus Torvalds (5/18/2011). "Linux 2.6.39". 
  7. Linus Torvalds (7/21/2011). "Linux 3.0". 
  8. Linus Torvalds (10/24/2011). "Linux 3.1". 
  9. Linus Torvalds (7/27/2011). "iSCSI merge". 
  10. Linus Torvalds (3/18/2012). "Linux 3.3". 
  11. Linus Torvalds (1/18/2012). "InfiniBand/SRP merge". 

Wikipedia entries

External links

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