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git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@367 d57e44dd-8a1f-0410-8b47-8ef2f437770f
183 lines
8.6 KiB
HTML
183 lines
8.6 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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<h1><small><a name="iscsi-scst"></a>ISCSI target driver iSCSI-SCST<br>
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</small></h1>
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<div style="text-align: justify;">
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<p>ISCSI-SCST is a forked (with all respects) version of <a
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href="http://iscsitarget.sourceforge.net/">IET</a> with
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updates to work over SCST as well as with many improvements and
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bugfixes. The reason of fork is that the necessary changes are
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intrusive and with the current IET merge policy, where only simple
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bugfix-like patches, which doesn't touch the core code, could be
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merged, it is very unlikely that they will be merged in the main IET
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trunk.<br>
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</p>
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<p>ISCSI-SCST has the following major advantages over the mainline IET:<br>
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</p>
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<ul>
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<li>It uses full SCST power without loosing any existing feature
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(except, maybe, "illegal" from SCSI specifications point of view MPIO).
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Namely, you can use with it:</li>
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</ul>
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<ul style="list-style-type: circle; margin-left: 40px;">
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<li>Pass-through mode with one to many relationship, i.e. when
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multiple initiators can connect to the exported pass-through devices.
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For instance, you can safely export your parallel SCSI
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tape or tape library on your iSCSI net and multiple initiators can
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share it without risk of data loss because of the shared usage.
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Existing "rawio" patch for IET supports only non-enforced 1:1
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relationship, so it is unsafe to use it in multiple initiators
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environments.<br>
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</li>
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<li>More advances devices visibility management, when different
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initiators can see different set of devices with different access
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permissions from the same target.</li>
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<li>O_DIRECT, i.e. "BLOCKIO on files", mode, which has all advantages
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of BLOCKIO, but also supports files on file systems. Sometimes, in the
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appropriate cases, this mode can make performance difference in 100% or
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even more.</li>
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<li>With 4KB blocks you can forget about abysmal write performance
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caused by misaligned partitions. All modern OS'es, including Windows
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starting from, at least, Windows 2000, work perfectly with 4KB block
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devices without any additional storage or handling overhead.</li>
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<li>Virtual CD/DVD-ROMs without necessity for manual patching.</li>
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<li>Ability to create target devices emulators in the user space.</li>
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<li>Ability to create multi-transport SCSI targets, which can export
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(possibly, the same) devices over multiple transports.</li>
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</ul>
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<ul>
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<li>It has many code improvements and cleanups, including stability
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and iSCSI RFC violations fixes. If you are an IET user and consider IET
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problemless, I'm sorry for the bad news. IET works well only on "fast"
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paths and regularly used branches, in many other less used cases IET
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has various problems, from simply ignoring error processing, as it is
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with memory allocations, to crashing itself with BUG() macro, as it is
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for malformed packets from initiators. ChangeLog file lists most
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noticeable fixes, but there were a lot of many other smaller ones.</li>
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</ul>
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<ul>
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<li>Due to its reworked IO architecture and SCST backend iSCSI-SCST
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has better performance in many cases. In future with upcoming SCST
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improvements, like zero-copy with Linux cache FILEIO, the performance
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difference is going to be even bigger. Currently in tests from a single
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initiator over a single connection on 1GbE hardware over FILEIO vdisk
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iSCSI-SCST with default settings usually outperforms tuned IET a on
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3-10% (by default IET has not too good settings, so it shows
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considerably worse results) or has the similar performance. The bigger
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difference is expected with 10GbE hardware or with higher number of
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initiators, since iSCSI-SCST has less commands processing overhead per
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command, hence has smaller processing latency and puts less load on
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CPU. If you find a case where
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iSCSI-SCST has worse performance, than IET, please report it to SCST
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mailing list, it will be greatly
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appreciated.</li>
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</ul>
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<p>Also, in contrast to IET, iSCSI-SCST is open for any new
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development, modifications and improvements, so people who want to fix
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or implement something new will not have to keep and maintain separate
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patches as it is currently necessary with IET. ISCSI-SCST is going to
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be actively developed and gain in the future new features like support
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for multiple connections per session, error recovery levels >0,
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etc., which eventually make it really "enterprise".<br>
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</p>
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<p>ISCSI-SCST is available for download from the <a
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href="http://scst.svn.sourceforge.net/">SCST SVN repository</a>. See
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the <a href="main.html">main page</a> how to setup access to it.<br>
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</p>
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<p>If you are an IET user before installation carefully read
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README files of both iSCSI-SCST and the SCST core. Especially pay
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attention that now the LUN information for iSCSI-SCST is configured not
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using iscsi-scstd.conf file in /etc, but using corresponding SCST
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facilities. This is because now the responsibilities are divided (as it
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should be) between the target driver (iSCSI-SCST) and the SCST core:
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target driver is responsible for handling targets and their
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parameters, SCST core is responsible for handling backstorage.<br>
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</p>
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</div>
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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><a name="qla2x00"></a>Target driver for QLogic 22xx/23xx
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cards<br>
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</small></h1>
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<div style="text-align: justify;">
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<p>This is target driver for QLogic 22xx/23xx Fibre Channel cards, but
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24xx and later cards are not supported by it.<br>
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</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 the <a href="main.html">main
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page</a> how to setup access to it.
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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
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released versions</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><a name="qla_isp"></a>Target driver for QLogic ISP chipsets<br>
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</small></h1>
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This is an SCST driver for ISP QLogic chipsets commonly used in many
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SCSI and FC host bus adapters. It is based on Matthew Jacob's
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multiplatform driver for ISP chipsets, which has its own page at <a
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href="http://www.feral.com/isp.html">http://www.feral.com/isp.html</a>.
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The update for SCST was made by Stanislaw Gruszka for Open-E Inc.<br>
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<br>
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Driver operates on the same hardware as the above target driver for
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QLogic 22xx/23xx cards, but has one notable advantage over it: support
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of 24xx series of QLogic adapters.<br>
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<br>
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This driver is in beta stages. You may want to use it in production,
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but you need to test it for your hardware configuration. It is
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available for download from the <a
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href="http://scst.svn.sourceforge.net/">SCST SVN repository</a>. See
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the <a href="main.html">main page</a> 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><a name="srpt"></a>Infiniband SCSI RDMA protocol (SRP)
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target driver</small></h1>
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SCSI RDMA Protocol (SRP) target driver is developed
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independently from SCST team. You can find instructions how to download
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and install it on its <a
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href="https://wiki.openfabrics.org/tiki-index.php?page=SRPT+Installation">wiki
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page</a>. Since March 2008 its main development place is <a
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href="http://scst.svn.sourceforge.net/">SCST SVN repository</a>.<br>
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<br>
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<hr style="width: 100%; height: 2px;">
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<h1><small><a name="fcoe"></a>Open-FCoE software target<br>
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</small></h1>
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<a href="http://www.open-fcoe.org/">Open-FCoE</a> is an open source
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project implementing the Fibre Channel over Ethernet for the Linux
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operating system. It uses SCST framework to implement software FC
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target.<br>
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<br>
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<hr style="width: 100%; height: 2px;">
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<h1><small><a name="lsi"></a>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. It supports parallel SCSI
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(SPI), but also should work with SAS and Fibre Channel transports. This
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driver is
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on the
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alpha stage and available for download from the <a
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href="http://scst.svn.sourceforge.net/">SCST SVN repository</a>. See
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the <a href="main.html">main page</a> how to setup access to it.<br>
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<br>
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<hr style="width: 100%; height: 2px;"><a href="main.html">Main</a> <a
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href="index.html">Index</a>
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</body>
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</html>
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