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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>Chapter 1. Introduction</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="SCSI Interfaces Guide" /><link rel="up" href="index.html" title="SCSI Interfaces Guide" /><link rel="prev" href="index.html" title="SCSI Interfaces Guide" /><link rel="next" href="ch01s02.html" title="Design of the Linux SCSI subsystem" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 1. Introduction</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="index.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="ch01s02.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 1. Introduction"><div class="titlepage"><div><div><h2 class="title"><a id="intro"></a>Chapter 1. Introduction</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="ch01.html#protocol_vs_bus">Protocol vs bus</a></span></dt><dt><span class="sect1"><a href="ch01s02.html">Design of the Linux SCSI subsystem</a></span></dt></dl></div><div class="sect1" title="Protocol vs bus"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="protocol_vs_bus"></a>Protocol vs bus</h2></div></div></div><p>
Once upon a time, the Small Computer Systems Interface defined both
a parallel I/O bus and a data protocol to connect a wide variety of
peripherals (disk drives, tape drives, modems, printers, scanners,
optical drives, test equipment, and medical devices) to a host
computer.
</p><p>
Although the old parallel (fast/wide/ultra) SCSI bus has largely
fallen out of use, the SCSI command set is more widely used than ever
to communicate with devices over a number of different busses.
</p><p>
The <a class="ulink" href="http://www.t10.org/scsi-3.htm" target="_top">SCSI protocol</a>
is a big-endian peer-to-peer packet based protocol. SCSI commands
are 6, 10, 12, or 16 bytes long, often followed by an associated data
payload.
</p><p>
SCSI commands can be transported over just about any kind of bus, and
are the default protocol for storage devices attached to USB, SATA,
SAS, Fibre Channel, FireWire, and ATAPI devices. SCSI packets are
also commonly exchanged over Infiniband,
<a class="ulink" href="http://i2o.shadowconnect.com/faq.php" target="_top">I20</a>, TCP/IP
(<a class="ulink" href="http://en.wikipedia.org/wiki/ISCSI" target="_top">iSCSI</a>), even
<a class="ulink" href="http://cyberelk.net/tim/parport/parscsi.html" target="_top">Parallel
ports</a>.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="index.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> <a accesskey="n" href="ch01s02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">SCSI Interfaces Guide </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Design of the Linux SCSI subsystem</td></tr></table></div></body></html>
