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272 lines
12 KiB
HTML
272 lines
12 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<html>
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<head>
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<meta http-equiv="content-type"
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content="text/html; charset=ISO-8859-1">
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<title>SCST: Generic SCSI Target Middle Level for Linux</title>
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<meta name="Keywords"
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content="SCST, Linux, SCSI target, Qlogic, QLA2200, QLA2300, iSCSI, SCSI">
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</head>
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<body>
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<a href="http://sourceforge.net"> <img
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src="http://sourceforge.net/sflogo.php?group_id=110471&type=5"
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alt="SourceForge.net Logo" border="0" height="62" width="210"></a>
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<h1><small>Generic SCSI Target Middle Level for Linux</small><br>
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</h1>
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<p style="text-align: justify;">The SCSI target mid-level subsystem for
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Linux (SCST) is a subsystem of the Linux kernel that provides a
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standard framework for SCSI target drivers development. It is designed
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to
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provide unified, consistent interface between SCSI target drivers and
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Linux kernel and simplify target drivers development as much as
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possible. A system with a SCSI target device is able to share its local
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or virtual devices with other systems on a network with SCSI protocol
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support, e.g. SCSI bus, Fibre Channel, TCP/IP with iSCSI. This is
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commonly used for data storage virtualization.<br>
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</p>
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<p style="text-align: justify;">SCST has the following features:</p>
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<div style="text-align: justify;">
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</div>
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<p style="text-align: justify;">
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</p>
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<div style="text-align: justify;">
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</div>
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<ul style="text-align: justify;">
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<li>Simple, easy to use interface with target drivers. Particularly,
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SCST performs all required pre- and post- processing of incoming
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requests and all necessary error recovery.</li>
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<li>Undertakes most problems, related to execution contexts, thus
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practically eliminating one of the most complicated problem in the
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kernel drivers development. For example, a target driver for Qlogic
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2200/2300 cards, which has all necessary features, is only ~2000 lines
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of code long.</li>
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<li> Very low overhead, fine-grained locks and simplest commands
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processing path, which allow to reach maximum possible performance and
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scalability. Particularly, incoming
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requests can be processed in the caller's context or in
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one of the internal SCST's tasklets, therefore no extra context
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switches
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required.</li>
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<li>Provides advanced per-initiator device visibility management (LUN
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masking),
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which allows different initiators see different set of devices
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with different access permissions. For instance, initiator A could see
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exported from
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target T devices Da and Db read-writable, and initiator B from the same
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target T could see devices Db read-only and Dc read-writable.<br>
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</li>
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<li> Complete SMP support.<br>
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</li>
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<li> Emulates necessary functionality of SCSI host adapter, because
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from a remote initiator's point of view SCST acts as a SCSI host with
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its
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own devices. Some of the emulated functions are the following:
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<ul>
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<li> Generation of necessary UNIT ATTENTIONs, their storage and
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delivery to all connected remote initiators (sessions). </li>
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<li> RESERVE/RELEASE functionality. </li>
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<li> CA/ACA conditions (not implemented yet). </li>
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<li> All types of RESETs and other task management functions. </li>
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<li> REPORT LUNS command as well as SCSI address space management
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in order to have consistent address space on all remote initiators,
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since local SCSI devices could not know about each other to report
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via REPORT LUNS command. Additionally, SCST responds with error on
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all commands to non-existing devices and provides access control, so
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different remote initiators could see
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different set of devices. </li>
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<li> Other necessary functionality (task attributes, etc.) as
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specified in SAM-2, SPC-2, SAM-3, SPC-3 and other SCSI standards. </li>
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</ul>
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</li>
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<li> Device handlers (i.e. plugins) architecture provides extra
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flexibility by allowing to make any additional
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requests processing, which is completely independent from target
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drivers and SCST core, like, for instance, device dependent exceptional
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conditions treatment, data caching or passing commands in the user
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space for device emulation. Example of such plugin is FILEIO device
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handler (see below) .<br>
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</li>
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<li>Well documented.<br>
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</li>
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</ul>
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<div style="text-align: justify;">
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</div>
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<p style="text-align: justify;">Interoperability between SCST and local
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SCSI initiators (like sd, st) is
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the additional issue that SCST is going to address (it is not
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implemented yet). It is necessary, because local SCSI initiators can
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change the state of the device, for example RESERVE the device, or some
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of its parameters and that would be done behind SCST, which could lead
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to various problems. Thus, RESERVE/RELEASE commands, locally generated
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UNIT ATTENTIONs, etc. should be intercepted and processed as if local
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SCSI initiators act as remote SCSI initiators connected to SCST. This
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feature requires some the kernel modification. Since in the current
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version it is not implemented, SCST and target drivers are
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able to work with any version of Linux 2.6 kernel.<br>
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</p>
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<p style="text-align: justify;">Interface between SCST and target
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drivers is based on work, done by <a href="http://www.iol.unh.edu/">University
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of New Hampshire Interoperability Labs (UNH IOL)</a> for the <a
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href="http://www.iol.unh.edu/consortiums/iscsi/index.html">UNH-iSCSI
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project</a>, which is currently developed on <a
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href="http://unh-iscsi.sourceforge.net/">SourceForge.net</a>.<br>
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</p>
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<p style="text-align: justify;">The latest stable version is 0.9.5. It
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supports SCSI disks (type 0), tapes (type 1), processors (type
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3), CDROMs (type 5), MO disks (type 7), medium changers (type 8) and
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RAID controllers (type 0xC). Also it supports FILEIO and "performance"
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device handlers. FILEIO device handler allows to use files on file
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systems or block devices as virtual remotely available SCSI disks or
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CDROMs. "Performance" device handlers provide a way for direct
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performance measurements without overhead of actual data transferring
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from/to underlying SCSI device. Requires Linux kernel 2.6.14 or higher.
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Tested mostly on i386 and x86_64,
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but should also
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work on any other
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supported by Linux platform. More detail information you could find in
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the project's README file.<br>
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</p>
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<p style="text-align: justify;">Starting from version 0.9.4 2.4 Linux
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kernels are not supported anymore, although there could be new SCST
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releases for those kernels with very important bug fixes. The latest
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stable
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version of SCST with 2.4 kernels support is 0.9.3.1-24.</p>
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<p style="text-align: justify;">If you have any questions you can ask
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them on the SCST SF.net page either using forum, or scst-devel mailing
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list.<br>
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</p>
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<a href="http://sourceforge.net/project/showfiles.php?group_id=110471">Download</a><br>
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<a href="http://www.sourceforge.net/projects/scst">SCST SF.net project
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page</a><br>
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<a href="ChangeLog.scst">Change Log</a><br>
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Documentation: <a href="doc/scst_pg.html">HTML</a>, <a
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href="doc/scst_pg.pdf">PDF</a><br>
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<p>The latest development versions of SCST and its drivers are
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available directly from the
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project's SVN. You can access it using either <a
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href="http://svn.sourceforge.net/scst">web-based SVN
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repository viewer</a> or using anonymous access: </p>
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<p> <tt> svn co https://svn.sourceforge.net/svnroot/scst<br>
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</tt></p>
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<p>More information about accessing SVN repository may be found <a
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href="http://sourceforge.net/docs/E09">here</a>.<br>
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</p>
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<p>History of the pre-SVN SCST development is available in SCST CVS
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repository, which is accessible using <a
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href="http://cvs.sourceforge.net/viewcvs.py/scst">web-based CVS
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repository viewer</a> or anonymous CVS access.<br>
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</p>
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<hr
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style="width: 100%; height: 2px; margin-left: 0px; margin-right: 0px;">
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<h1><small>SCST administration utility<br>
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</small></h1>
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<p>SCST administration utility "scstadmin" is developed by Mark
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Buechler. With it you can manually or automatically using either plain
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text config file, or MySQL database configure every aspect of SCST, for
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instance as part of the system startup/shutdown, including
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enabling/disabling target mode on your target SCSI controller.<br>
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</p>
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<p><a
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href="http://sourceforge.net/project/showfiles.php?group_id=110471">Download</a>
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</p>
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<hr
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style="width: 100%; height: 2px; margin-left: 0px; margin-right: 0px;">
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<h1><small>Target driver for Qlogic 2200/2300 cards for 2.6 kernels<br>
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</small></h1>
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<div style="text-align: justify;">
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<p>This is ported and improved version of the "old" target driver for
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2.4 kernels (see below) to the in-tree 2.6
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Qlogic 2x00 initiator
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driver. The port was done by Nathaniel Clark. This is stable and
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functional driver with
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the larger feature set, than the parent driver has.</p>
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<p style="text-align: justify;">The latest version is 0.9.5. Requires
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Linux kernel version 2.6.16.x or higher and SCST version 0.9.5 or
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higher.
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Tested mostly on i386 and
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x86_64, but
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should work on any other supported by Linux platform.
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</p>
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<p style="text-align: justify;">You can find the latest development
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version of this driver in the SCST SVN. See above how to setup access
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to it.<br>
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</p>
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<p style="text-align: justify;"><a
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href="http://sourceforge.net/project/showfiles.php?group_id=110471">Download</a><br>
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<a href="ChangeLog.qla26">Change Log</a><br>
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</p>
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</div>
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<hr style="width: 100%; height: 2px;">
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<h1><small>Target driver for LSI/MPT cards</small></h1>
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Target driver LSI/MPT cards was originally developed by Hu Gang, then
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Erik Habbinga has continued the development. This driver is on the
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alpha stage and available from the <a
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href="http://svn.sourceforge.net/scst">SCST SVN repository</a>. See
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above how to setup access to it.<br>
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<br>
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<hr style="width: 100%; height: 2px;">
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<h1><small>Old target driver for Qlogic 2200/2300 cards<br>
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</small></h1>
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<div style="text-align: justify;">Old target driver for Qlogic
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2200/2300
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cards is capable to work on 2.4 kernels. It has all required features
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and
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looks to be quite stable. It is designed to work in conjunction with
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the initiator
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driver, which is intended to perform all the initialization and
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shutdown tasks. In the current release as a base for the initiator
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driver was taken Red Hat's driver from the stock 2.4.20 kernel. Then it
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was patched to enable the target mode and provide all
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necessary callbacks, and it's still able to work as initiator only.
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Mode, when a host acts as the initiator and the target simultaneously,
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is also supported. This driver is obsoleted in favor of
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2.6-based driver (see above).<br>
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<br>
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The latest version is 0.9.3.4. Requires Linux kernel versions 2.4.20 or
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higher and SCST version 0.9.3-pre4 or higher. If you are lucky, it
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works also on 2.6 kernels, see README file
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for details. Tested on i386 only, but
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should work on any other supported by Linux platform.<br>
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<br>
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</div>
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<a href="http://sourceforge.net/project/showfiles.php?group_id=110471">Download</a><br>
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<a href="ChangeLog.qla">Change Log</a>
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<hr style="width: 100%; height: 2px;"><span style="font-weight: bold;"></span>
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<h1><small>Target drivers for Adaptec 7xxx and Qlogic QLA12xx
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cards</small></h1>
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Target drivers for Adaptec 7xxx and Qlogic QLA12xx cards have
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been developed by Hu Gang and they available for download from <a
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href="http://bj.soulinfo.com/%7Ehugang/scst/tgt/">http://bj.soulinfo.com/~hugang/scst/tgt/</a>.
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These drivers are not completed, but looks to be a good starting point
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if you are going to use one of these cards.
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SCST team don't have the appropriate hardware, therefore have not
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tested and don't support these drivers. Send all questions to Hu Gang
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<hugang
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% soulinfo.com>. If some of these drivers don't compile for you, try
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again with SCST version 0.9.3-pre2.<br>
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<br>
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<a href="http://bj.soulinfo.com/%7Ehugang/scst/tgt/">Download</a><br>
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<br>
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<hr style="width: 100%; height: 2px;">
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<h1><small>Patches for UNH-iSCSI Target 1.5.03 and 1.6.00 to work over
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SCST</small></h1>
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SCST is much more advanced, than the internal mid-level of <a
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href="http://sourceforge.net/projects/unh-iscsi">UNH-iSCSI target
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driver</a>.
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With SCST the iSCSI target benefits from all its features and gets
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ability to use all its advantages, like high performance and
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scalability, SMP support, required SCSI functionality emulation, etc.<br>
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<br>
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Since the interface between SCST and the target drivers is based on
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work, done by UNH IOL, it was relatively simple to update UNH-iSCSI
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target to work over SCST. Mostly it was "search and replace" job. The
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built-in scsi_target remains available as a compile-time option.<br>
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<br>
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Requires Linux kernel versions 2.4.20 or
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higher or 2.6.7 or higher and SCST version 0.9.2 or higher.<br>
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<br>
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<a href="http://sourceforge.net/project/showfiles.php?group_id=110471">Download</a><br>
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<br>
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</body>
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</html>
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