mirror of
https://github.com/SCST-project/scst.git
synced 2026-05-23 21:51:27 +00:00
fec41c57ab
git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@750 d57e44dd-8a1f-0410-8b47-8ef2f437770f
345 lines
24 KiB
HTML
345 lines
24 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
|
|
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
|
|
<head>
|
|
<meta name="Keywords" content="Generic SCSI Target Middle Level for Linux" />
|
|
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
|
|
<meta name="author" content="Daniel Fernandes"/>
|
|
<meta name="Robots" content="index,follow" />
|
|
<link rel="stylesheet" href="images/Orange.css" type="text/css" />
|
|
<title>SCST: Generic SCSI Target Middle Level for Linux</title>
|
|
</head>
|
|
|
|
<body>
|
|
<!-- wrap starts here -->
|
|
<div id="wrap">
|
|
<div id="header">
|
|
<div class="logoimg"></div><h1 id="logo"><span class="orange"></span></h1>
|
|
<h2 id="slogan">SCSI Target Middle Level for Linux</h2>
|
|
</div>
|
|
|
|
<div id="menu">
|
|
<ul>
|
|
<li id="sponsorship"><a href="sponsorship.html">Sponsorship</a></li>
|
|
<li><a href="index.html">Home</a></li>
|
|
<li><a href="http://www.sourceforge.net/projects/scst">Main</a></li>
|
|
<li><a href="targets.html">Drivers</a></li>
|
|
<li><a href="downloads.html">Downloads</a></li>
|
|
<li><a href="contributing.html">Contributing</a></li>
|
|
<li id="current"><a href="comparison.html">Comparison</a></li>
|
|
</ul>
|
|
</div>
|
|
|
|
<!-- content-wrap starts here -->
|
|
<div id="content-wrap">
|
|
<div id="sidebar">
|
|
<h1>Target Drivers</h1>
|
|
<ul class="sidemenu">
|
|
<li><a href="comparison.html">Features comparison</a></li>
|
|
<li><a href="scstvsstgt.html">SCST vs STGT</a></li>
|
|
</ul>
|
|
</div>
|
|
|
|
<div id="main">
|
|
<h1>Features comparison between Linux SCSI targets</h1>
|
|
|
|
<p><small>As on April 2009</small></p>
|
|
|
|
<table bgcolor="#F0F0F0" border="1" cols="5" cellspacing="1" cellpadding="7" style="text-align:center" width="620">
|
|
|
|
<tr>
|
|
<th>
|
|
</th><th> <a href="http://scst.sourceforge.net/" title="http://scst.sourceforge.net/" rel="nofollow">SCST</a>
|
|
</th><th> <a href="http://stgt.berlios.de/" title="http://stgt.berlios.de/" rel="nofollow">STGT</a>
|
|
</th><th> <a href="http://iscsitarget.sourceforge.net/" title="http://iscsitarget.sourceforge.net/" rel="nofollow">IET</a>
|
|
</th><th> <a href="http://linux-iscsi.org/" title="http://linux-iscsi.org/" rel="nofollow">LIO v3.0</a>
|
|
</th></tr>
|
|
|
|
<tr bgcolor="#E0E0E0">
|
|
<td colspan="5"> <b>General</b>
|
|
</td></tr>
|
|
<tr>
|
|
<th align="left"> Upstream kernel</th> <td> - </td> <td> Kernel part </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Generic Target Engine </th> <td> + </td> <td> + </td> <td> iSCSI only </td> <td> Under development </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Architecture </th> <td> Kernel only</td> <td> User space only
|
|
<sup><A HREF="#1">1</A>
|
|
</sup> </td> <td> Split <sup>
|
|
<A HREF="#2">2</A>
|
|
</sup> </td> <td> Kernel only </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Stability </th> <td> + </td> <td> + </td> <td> + </td> <td> Heavy development </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Performance </th> <td> ***** </td> <td> ***</td> <td> **** </td> <td> ****
|
|
<sup><A HREF="#3">3</A></sup></td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Zero-Copy </th> <td> **** </td> <td> ***
|
|
<sup><A HREF="#4">4</A>
|
|
</sup> </td> <td> **** </td> <td> **** </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Support for transports without expecting
|
|
transfer values (parallel SCSI, SAS) </th> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> User Interface </th> <td> ProcFS </td> <td> Custom </td> <td> IOCTL/ProcFS </td> <td> ConfigFS/IOCTL </td>
|
|
</tr>
|
|
|
|
|
|
<tr bgcolor="#E0E0E0">
|
|
<td colspan="5"> <b>Major features</b>
|
|
</td></tr>
|
|
<tr>
|
|
<th align="left"> Target drivers in kernel space </th> <td> + </td> <td> + </td> <td> - </td> <td> Under development </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Target drivers in user space </th> <td> + </td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Backstorage handlers in kernel space </th> <td> + </td> <td> - </td> <td> - </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Backstorage handlers in user space </th> <td> + </td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Local access to emulated backstorage devices</th> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Advanced devices visibility management </th> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Support for Asynchronous Event Notifications
|
|
(AEN) </th> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> AEN for devices added/removed</th> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> AEN for devices resized</th> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Bidirectional Commands </th> <td> + <sup>
|
|
<A HREF="#5">5</A>
|
|
</sup></td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Extended CDB (size >16 bytes) </th> <td> + <sup>
|
|
<A HREF="#5">5</A>
|
|
</sup></td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Descriptor sense support </th> <td> + </td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<th align="left"> RESERVE/RELEASE
|
|
<small> (Windows 2003 clustering) </small></th> <td> + </td> <td> + </td> <td> + </td> <td> + </td>
|
|
</tr>
|
|
<th align="left"> Safe RESERVE/RELEASE implementation according to
|
|
SCSI requirements <sup><A HREF="#6">6</A></sup></th> <td> Safe </td> <td> Safe </td> <td> Not safe </td> <td> Not safe </td>
|
|
</tr>
|
|
<th align="left"> Safe implementation of Task Management commands
|
|
<sup><A HREF="#7">7</A></sup></th> <td> Safe </td> <td> Not safe </td> <td> Not safe </td> <td> Not safe </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Persistent Reservations <br/>
|
|
<small> (Windows 2008 clustering)</small></th> <td> - </td> <td> - </td> <td> - </td> <td> Under development </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> ALUA </th> <td> - </td> <td> - </td> <td> - </td> <td> Under development </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Failover Clustering </th> <td> + </td> <td> ? </td> <td> + </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> SCSI MIBs </th> <td> - </td> <td> - </td> <td> - </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Cluster Storage Integration </th> <td> - </td> <td> - </td> <td> - </td> <td> VHACS </td>
|
|
</tr>
|
|
|
|
|
|
<tr bgcolor="#E0E0E0">
|
|
<td colspan="5"> <b>Supported SCSI transports</b>
|
|
</td></tr>
|
|
<tr>
|
|
<th align="left"> iSCSI </th> <td> + </td> <td> + </td> <td> + </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Fibre Channel </th> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> SRP </th> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> iSER </th> <td> - </td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Parallel (Wide) SCSI </th> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> SAS </th> <td> Under
|
|
development </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> FCoE </th> <td> Under
|
|
development </td> <td>Under
|
|
development</<td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> IBM pSeries Virtual SCSI </th> <td> - </td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
|
|
<tr bgcolor="#E0E0E0">
|
|
<td colspan="5"> <b>Supported backstorage</b>
|
|
</td></tr>
|
|
<tr>
|
|
<th align="left"> Kernel side FILEIO </th> <td> + </td> <td> - </td> <td> + </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Kernel side BLOCKIO </th> <td> + </td> <td> - </td> <td> + </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> User space side FILEIO </th> <td> + </td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> SCSI Pass-through </th> <td> + </td> <td> - </td> <td> - </td> <td> Single initiator only, not enforced
|
|
<sup><A HREF="#8">8</A></sup></td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> 4k sectors support in pass-through mode </th> <td> + </td> <td> - </td> <td> - </td> <td> ? </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> 4k, 2k, 1k and 512 byte sectors emulation
|
|
in modes, other than pass-through </th> <td> + </td> <td> - </td> <td> - </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> CDROM emulation from ISO files </th> <td> + </td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
|
|
<tr bgcolor="#E0E0E0">
|
|
<td colspan="5"> <b>iSCSI Target</b>
|
|
</td></tr>
|
|
<tr>
|
|
<th align="left"> Architecture </th> <td> Split <sup>
|
|
<A HREF="#2">2</A>
|
|
</sup> </td> <td> User space
|
|
only </td> <td> Split <sup>
|
|
<A HREF="#2">2</A>
|
|
</sup></td> <td> Kernel only </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> MC/S </th> <td> - </td> <td> - </td> <td> - </td> <td> + </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Max ErrorRecoveryLevel </th> <td> 0 </td> <td> 0 </td> <td> 0 </td> <td> 2 </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Bidirectional Commands </th> <td> + <sup>
|
|
<A HREF="#5">5</A>
|
|
</sup></td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Extended CDB (size >16 bytes) </th> <td> + <sup>
|
|
<A HREF="#5">5</A>
|
|
</sup></td> <td> + </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> Support for Asynchronous Event Notifications
|
|
(AEN) </th> <td> + </td> <td> - </td> <td> - </td> <td> - </td>
|
|
</tr>
|
|
<th align="left"> Safe implementation of connections and sessions
|
|
reinstatement <sup><A HREF="#9">9</A></sup></th> <td> Safe </td> <td> Not safe </td> <td> Not safe </td> <td> Not safe </td>
|
|
</tr>
|
|
<tr>
|
|
<th align="left"> iSCSI MIBs </th> <td> - </td> <td> - </td> <td> - </td> <td> -
|
|
<sup><A HREF="#10">10</A></sup></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<br/>
|
|
<p><strong><big><u>REMARKS:</u></big></strong></p>
|
|
|
|
<p><A NAME="1"></A> 1. STGT has SCSI target engine in user space and small hooks in the kernel to interact with in-kernel target drivers.</p>
|
|
|
|
<p><A NAME="2"></A> 2. All iSCSI management implemented in user space and actual data transfers in kernel space without user space involved.</p>
|
|
|
|
<p><A NAME="3"></A> 3. The conclusion made by source code study only. LIO should have performance
|
|
on the IET level or slightly less, because of more processing overhead. </p>
|
|
|
|
<p><A NAME="4"></A> 4. Some zero-copy functionality isn't available from user space. For instance, zero-copy send to a socket.</p>
|
|
|
|
<p><A NAME="5"></A> 5. Not well tested, because at the moment there is no backend using this functionality.</p>
|
|
|
|
<p><A NAME="6"></A> 6. SCSI requires that if an initiator clears reservation held by another initiator, the reservation holder must be notified
|
|
about the reservation clearance. Otherwise, several initiators can at the same time change supposed to be protected by the
|
|
reservation data, which can corrupt them.</p>
|
|
|
|
<p><A NAME="7"></A> 7. After a task management command completed and corresponding response was sent to initiator, who sent that task management
|
|
command, all the affected SCSI commands must get into a state, where they can't affect following after
|
|
the tasks management response commands from this initiator. This is the safe implementation.
|
|
The unsafe implementation only marks all the affected
|
|
SCSI commands as aborted and then immediately send task management response to the initiator. This implementation only
|
|
guarantees that the initiator will never receive responses from those commands, but it doesn't
|
|
guarantee that none of those commands will get executed by backstorage <strong>*AFTER*</strong> any
|
|
SCSI command, which initiator will send after it received the task management response thinking
|
|
that all the aborted commands actually fully aborted. This could lead to a data corruption.</p>
|
|
|
|
<p><A NAME="8"></A> 8. LIO doesn't emulate all the necessary SCSI host functionality to allow to share a SCSI device
|
|
in pass-through mode to several initiators. It can only pass SCSI commands from initiator to
|
|
the SCSI device. This is safe only if there is only one initiator. This limitation
|
|
isn't enforced anyhow by LIO. You can find more technical information about that in
|
|
<a href="http://www.mail-archive.com/linux-scsi@vger.kernel.org/msg06911.html">
|
|
http://www.mail-archive.com/linux-scsi@vger.kernel.org/msg06911.html</a></p>
|
|
|
|
<p><A NAME="5"></A> 9. Connections and sessions reinstatement is, basically, a kind of Task Management command.
|
|
For instance, open-iscsi uses it as such in eh_target_reset_handler() callback. So, similarly
|
|
to <A HREF="#7">(7)</A> above, a safe implementation
|
|
must not accept SCSI commands from new connection/session until all the SCSI commands in
|
|
being reinstated connection/session get into a state, where they can't affect the new commands.</p>
|
|
|
|
<p><A NAME="10"></A> 10. SCSI-MIB (RFC 4455) - not supported;
|
|
SBE-SCSI-MIB - supported by LIO v2.6, not supported by LIO v3.0;
|
|
SBE-ISCSI-MIB - supported by LIO v2.6, not supported by LIO v3.0;
|
|
SBE-IPS-AUTH-MIB - supported by LIO v2.6, not supported by LIO v3.0
|
|
|
|
</p>
|
|
|
|
<br/>
|
|
<hr style="width: 100%; height: 1px; margin-left: 15px; margin-right: 0px;">
|
|
<br/>
|
|
|
|
<p><strong>P.S.</strong> LIO has similar comparison
|
|
<a href="http://www.linux-iscsi.org/index.php/Overview_Page">page</a>. It is very much
|
|
wrong about SCST. I asked that page author, Nicholas Bellinger, to
|
|
correct the wrong items (see <a href="http://sourceforge.net/mailarchive/forum.php?thread_name=49AECE0B.5030009%40vlnb.net&forum_name=scst-devel">my e-mail</a>),
|
|
but Nicholas Bellinger refused to do it. Moreover, he blocked my access
|
|
to the LIO mailing list, preventing me from tell that to the interested
|
|
people myself. After all our previous discussions and with his skills
|
|
and experience I can't believe that Nicholas Bellinger doesn't know that
|
|
SCST is a lot more generic than LIO and has zero-copy in all the same
|
|
places, where LIO has. So, that comparison page looks like rather a
|
|
deliberate cheating attempt. Definitely, SCST in all major
|
|
technical areas is so much superior over LIO, so Nicholas Bellinger started
|
|
attacking people's perception about SCST trying to inspire them the
|
|
opposite.</strong></p>
|
|
|
|
</div>
|
|
</div>
|
|
</div>
|
|
<!-- wrap ends here -->
|
|
|
|
<!-- footer starts here -->
|
|
<div id="footer">
|
|
<p>
|
|
© Copyright 2008 <b><font color="#EC981F">Vladislav Bolkhovitin & others.</font>
|
|
Design by: <b><font color="#EC981F">Daniel Fernandes</font></b>
|
|
|
|
</p>
|
|
</div>
|
|
<!-- footer ends here -->
|
|
</body>
|
|
</html>
|