Comparison page updates
authorvlnb <vlnb@d57e44dd-8a1f-0410-8b47-8ef2f437770f>
Mon, 6 Apr 2009 15:14:55 +0000 (15:14 +0000)
committervlnb <vlnb@d57e44dd-8a1f-0410-8b47-8ef2f437770f>
Mon, 6 Apr 2009 15:14:55 +0000 (15:14 +0000)
git-svn-id: https://scst.svn.sourceforge.net/svnroot/scst/trunk@754 d57e44dd-8a1f-0410-8b47-8ef2f437770f

www/comparison.html
www/comparison_history.html [new file with mode: 0644]

index 4887920..dc63177 100644 (file)
                                                                                                                        </sup> </td>            <td> Kernel only </td>
 </tr>                                                                                                                           
 <tr>                                                                                                                           
-<th align="left"> Stability </th>                                      <td> + </td>            <td> + </td>            <td> + </td>            <td> Heavy development </td>
+<th align="left"> Stability </th>                                      <td> + </td>            <td> +
+                                                                                               <sup><A HREF="#3">3</A> 
+                                                                                               </sup> </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>
+<th align="left"> Performance <sup><A HREF="#4">4</A></sup></th>       <td> ***** <sup>
+                                                                       <A HREF="#5">5</A>
+                                                                       </sup></td>             <td> ***</td>           <td> **** </td>         <td> ****
+                                                                                                                                               <sup><A HREF="#6">6</A></sup></td>
 </tr>                                                                                                                           
 <tr>                                                                                                                           
 <th align="left"> Zero-Copy </th>                                      <td> **** </td>         <td> *** 
-                                                                                               <sup><A HREF="#4">4</A> 
+                                                                                               <sup><A HREF="#7">7</A> 
                                                                                                </sup> </td>            <td> **** </td>         <td> **** </td>         
 </tr>
 <tr>                                                                                            
@@ -87,7 +91,7 @@
 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>
+<th align="left"> User Interface </th>                                 <td> ProcFS </td>       <td> Custom </td>       <td> IOCTL/ProcFS </td> <td> ConfigFS/IOCTL/ProcFS </td>
 </tr>                                                                                                                           
 
                                                                                                 
@@ -107,10 +111,12 @@ transfer values (parallel SCSI, SAS) </th>                                <td> + </td>            <td> - </td>            <td> -
 <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>
+<th align="left"> Local access to emulated backstorage devices 
+<sup><A HREF="#8">8</A></sup></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>
+<th align="left"> Advanced devices visibility management 
+<sup><A HREF="#9">9</A></sup></th>                                     <td> + </td>            <td> - </td>            <td> - </td>            <td> - </td>
 </tr>
 <tr>                                                                                            
 <th align="left"> Support for Asynchronous Event Notifications
@@ -124,12 +130,12 @@ transfer values (parallel SCSI, SAS) </th>                                <td> + </td>            <td> - </td>            <td> -
 </tr>
 <tr>                                                                                                                            
 <th align="left"> Bidirectional Commands </th>                         <td> + <sup>
-                                                                       <A HREF="#5">5</A>
+                                                                       <A HREF="#10">10</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>
+                                                                       <A HREF="#10">10</A>
                                                                        </sup></td>             <td> + </td>            <td> - </td>            <td> - </td>
 </tr>
 <tr>                                                                                            
@@ -139,10 +145,10 @@ transfer values (parallel SCSI, SAS) </th>                                <td> + </td>            <td> - </td>            <td> -
 <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>
+SCSI requirements <sup><A HREF="#11">11</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>
+<sup><A HREF="#12">12</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/>
@@ -155,7 +161,8 @@ SCSI requirements <sup><A HREF="#6">6</A></sup></th>                        <td> Safe </td>         <td> Saf
 <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>            
+<th align="left"> SCSI MIBs </th>                                      <td> - </td>            <td> - </td>            <td> - </td>            <td>  - 
+                                                                                                                                               <sup><A HREF="#13">13</A></sup></td>
 </tr>                                                                                                                           
 <tr>                                                                                                                            
 <th align="left"> Cluster Storage Integration </th>                    <td> - </td>            <td> - </td>            <td> - </td>            <td> VHACS </td>        
@@ -207,7 +214,7 @@ SCSI requirements <sup><A HREF="#6">6</A></sup></th>                        <td> Safe </td>         <td> Saf
 </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>
+                                                                                                                                               <sup><A HREF="#14">14</A></sup></td>
 </tr>                                                                                           
 <tr>                                                                                                                            
 <th align="left"> 4k sectors support in pass-through mode </th>                <td> + </td>            <td> - </td>            <td> - </td>            <td> ? </td>
@@ -232,19 +239,19 @@ in modes, other than pass-through </th>                                   <td> + </td>            <td> - </td>            <td> - <
                                                                                                                        </sup></td>             <td> Kernel only </td>
 </tr>
 <tr>                                                                                                                            
-<th align="left"> MC/S </th>                                           <td> - </td>            <td> - </td>            <td> - </td>            <td> + </td>
+<th align="left"> Multiple connections per session (MS/C) </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>
+                                                                       <A HREF="#10">10</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>
+                                                                       <A HREF="#10">10</A>
                                                                        </sup></td>             <td> + </td>            <td> - </td>            <td> - </td>
 </tr>
 <tr>                                                                                            
@@ -252,33 +259,56 @@ in modes, other than pass-through </th>                                   <td> + </td>            <td> - </td>            <td> - <
 (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>
+reinstatement <sup><A HREF="#15">15</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>
+                                                                                                                                               <sup><A HREF="#13">13</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="1"></A> 1. STGT has SCSI target engine with memory management 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="3"></A> 3. ISER target driver has long known (since Feb 2008) data corruption problem, which localization hasn't been determined yet and might be
+                      in the STGT core. See <a href="http://lists.berlios.de/pipermail/stgt-devel/2008-February/001367.html">
+                      http://lists.berlios.de/pipermail/stgt-devel/2008-February/001367.html</a> and
+                      <a href="http://lists.wpkg.org/pipermail/stgt/2009-February/002630.html">http://lists.wpkg.org/pipermail/stgt/2009-February/002630.html</a></p>
+
+<p><A NAME="4"></A> 4. The result "in average" is listed. One target can be better somewhere, another one somewhere else. Although manual tuning of target and
+                      system parameters tends the restore the difference listed in the comparison.</p>
+
+<p><A NAME="5"></A> 5. All SCST and its drivers' kernel patches supposed to be applied and SCST with the drivers built in the release or performance build.
+                      Without the kernel patches SCST performance will be at "****+" level, except for the case, when user space backstorage handler used
+                      with iSCSI-SCST iSCSI target driver, where performance will be at "***+" level.</p>
+
+<p><A NAME="6"></A> 6. There is no performance data for LIO, which allow to make a direct comparison of it with other targets.
+                      The conclusion was made by source code study only. LIO should have performance on the IET level or less,
+                      because of more processing overhead. It might be much less for small block sizes.</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="7"></A> 7. 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="8"></A> 8. "Local access to emulated backstorage devices" means that you can access emulated by a SCSI target devices
+                      locally on the target host. For instance, you can mount your ISO image as a SCSI CDROM device locally on the
+                      target host.</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
+<p><A NAME="9"></A> 9. "Advanced devices visibility management" means that different initiators can see different sets
+                      of devices from the same target. This feature is essential with hardware targets, which don't have a possibility
+                      to create virtual targets.</p>
+
+<p><A NAME="10"></A> 10. Not well tested, because at the moment there is no backend using this functionality.</p>
+
+<p><A NAME="11"></A> 11. 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>
+                      reservation data, which can corrupt them. This is what was called 
+                      <a href="http://communities.vmware.com/thread/53797?tstart=0&start=15">"Russian roulette with your data"</a> by someone
+                      working for VMware on the VMware community forum.</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
+<p><A NAME="12"></A> 12. After a task management command completed and before the corresponding response was sent to the 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
@@ -288,44 +318,24 @@ reinstatement <sup><A HREF="#9">9</A></sup></th>                  <td> Safe </td>         <td> Not saf
                       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
+<p><A NAME="13"></A> 13. The IETF SCSI-MIB (RFC 4455) is not supported by LIO, only proprietary MIBs SBE-SCSI-MIB, SBE-ISCSI-MIB and SBE-IPS-AUTH-MIB are supported.
+
+<p><A NAME="14"></A> 14. 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
+<p><A NAME="15"></A> 15. Connections and sessions reinstatement is, basically, a kind of Task Management command, because it implies commands aborting.
+                      For instance, open-iscsi uses it as a less intrusive substistute for target reset 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>
+<p><small><strong>P.S.</strong> You can find a brief background history of this comparison page <a href="comparison_history.html">here</a>.</small></p>
 
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+<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">\r
+<head>\r
+<meta name="Keywords" content="Generic SCSI Target Middle Level for Linux" />\r
+<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />\r
+<meta name="author" content="Daniel Fernandes"/>\r
+<meta name="Robots" content="index,follow" />\r
+<link rel="stylesheet" href="images/Orange.css" type="text/css" />     \r
+<title>SCST: Generic SCSI Target Middle Level for Linux</title>\r
+</head>\r
+\r
+<body>\r
+<!-- wrap starts here -->\r
+<div id="wrap"> \r
+       <div id="header">       \r
+               <div class="logoimg"></div><h1 id="logo"><span class="orange"></span></h1>\r
+               <h2 id="slogan">SCSI Target Middle Level for Linux</h2> \r
+       </div>          \r
+               \r
+       <div id="menu">\r
+               <ul>\r
+                       <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>\r
+                       <li><a href="targets.html">Drivers</a></li>\r
+                       <li><a href="downloads.html">Downloads</a></li>\r
+                       <li><a href="contributing.html">Contributing</a></li>\r
+                       <li id="current"><a href="comparison.html">Comparison</a></li>          \r
+               </ul>\r
+       </div>\r
+       \r
+       <!-- content-wrap starts here -->       \r
+       <div id="content-wrap">  \r
+                       <div id="sidebar">\r
+                               <h1>Target Drivers</h1>\r
+                               <ul class="sidemenu">
+                                       <li><a href="comparison.html">Features comparison</a></li>
+                                       <li><a href="scstvsstgt.html">SCST vs STGT</a></li>
+                               </ul>
+                       </div>          \r
+       
+                       <div id="main">
+
+<h3>Some background history of the <a href="comparison.html">Features comparison</a> page.</h3>
+
+<p>LIO was the first who has had similar comparison page
+http://www.linux-iscsi.org/index.php/Overview_Page. It was and still 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 without any explanations. 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 it's nearly impossible to believe that Nicholas Bellinger
+didn'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 looked
+like rather a deliberate cheating attempt and for SCST there was no other way, except to setup own, correct comparison.
+This comparison table turned out to be very useful, so it was extended to cover all the SCSI target areas.</p>
+
+                       </div> \r
+       </div>\r
+</div>         \r
+<!-- wrap ends here -->\r\r
+<!-- footer starts here -->            \r
+               <div id="footer">\r
+                       <p>\r
+                       &copy; Copyright 2008 <b><font color="#EC981F">Vladislav Bolkhovitin & others.</font>&nbsp;&nbsp;\r
+                       Design by: <b><font color="#EC981F">Daniel Fernandes</font></b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;         \r
+                       \r
+                       </p>            \r
+               </div>  \r
+<!-- footer ends here -->\r
+</body>\r
+</html>