LIO Unified Target

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LIO Unified Target
Basic data

developer Datera
Current  version 4.0.0
(December 17, 2010)
operating system Linux
category SCSI
License GPL
www.linux-iscsi.org

" LIO Unified Target" is a multi-protocol capable SCSI target module for the Linux kernel from version 2.6.38. It replaces the previous STGT target. LIO currently supports the protocols iSCSI , Fiber Channel , FCoE and InfiniBand (SRP and iSER). In addition to the x86 microprocessor architecture, IA-64 , ARM , MIPS and IBM POWER are supported. The concept of the unified target module is primarily required for access to a large number of storage media via a large number of protocols. As a unified target module, LIO neither accesses data itself, nor does it communicate directly with the applications. The task of LIO is to seamlessly abstract the semantics of various SCSI targets.

architecture

LIO architecture

SCSI target module

LIO has a modular structure around a central SCSI target module. In this context, the term SCSI target is not only used for service-providing devices on a SCSI bus, but also in general for the command-receiving side of a SCSI connection, i.e. also for SCSI connections that operate over networks without a physical SCSI bus work. In this case, the SCSI target module is the server providing the service for these connections.

Backstores

In order to be able to provide this service, the SCSI target module requires storage media which, depending on the design, can in turn be SCSI targets, but do not have to be. The connection to a large number of different storage media is provided by so-called backstores , which work as a backend on the SCSI target module. Backstores can be connected to the SCSI target module via an interface for the abstraction of storage devices of the Storage Hardware Abstraction Layer (S-HAL) in the Linux kernel. The SCSI target module supports the SCSI-3 standard for all backstores . A special loopback module allows the integration of RAM disks or SSD memories. Files from any file system can be integrated as a storage medium via the FILEIO module.

Fabric modules

A fabric module (eng. "Tissue" or "structure") provides the services of the SCSI target module via a specific protocol. There are fabric modules for Fiber Channel , FCoE (Fiber Channel over Ethernet ) SCSI over IP networks and others. This enables so-called storage area networks (SAN) to be set up.

initiator

In addition to the SCSI target, Datera also provides an open source iSCSI initiator called Core-iSCSI . A special feature is the support of multiple connections per session (Multiple iSCSI connections per iSCSI session - MC / S). This enables improved availability and throughput. The standard Linux iSCSI initiator does not support this feature. Core iSCSI also allows the booting of servers via an iSCSI SAN (diskless boot).

Features

LIO supports the iSCSI standard as well as persistent reservations and ALUAs (Asymmetric Logical Unit Assignment) of the SPC-4 SCSI standard.

Together with the replication software DRBD and the cluster software Corosync , high-availability storage systems can be set up. The RTSdirector implements its own multinode cluster with linear scalability.

The configuration takes place via the Linux configfs, the administration via a command line tool (RTSadmin). With the release of version 2 it is possible to administrate Fiber Channel , FCoE and InfiniBand configurations. Version 2 was licensed in two ways and the community version 'targetcli' was published under the AGPL .

LIO was developed by the company Datera and is integrated by some manufacturers of storage systems ("storage appliances") ( Buffalo , Netgear , Pure Storage, QNAP , Synology etc.).

Web links

Individual evidence

  1. ↑ Linus Torvalds: Trivial merge . lkml.org. January 15, 2011. Retrieved on March 7, 2011.  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: dead link / git.kernel.org  
  2. ↑ Thorsten Leemhuis: Kernel-Log - What 2.6.38 brings (4): Storage . Heise open source. February 28, 2011. Retrieved March 7, 2011.
  3. ↑ STGT Target
  4. ↑ LIO target . linux-iscsi.org. Retrieved August 26, 2012.
  5. ↑ RFC 3720
  6. ^ Ralph Weber: SCSI Primary Commands - 4 (SPC-4) . t10.org. January 17, 2011. Retrieved March 7, 2011.
  7. ↑ Jonathan Corbet: Configfs - an introduction . lwn.net. August 24, 2005. Retrieved March 7, 2011.
  8. ↑ targetcli . linux-iscsi.org. Retrieved February 29, 2012.