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35                                 <h1>SCST vs STGT</h1>\r
36                                 <p><strong><a href="http://stgt.berlios.de/">STGT</a></strong> is alternative, independent from SCST implementation 
37                                 of SCSI target framework for Linux. It has different architecture, where SCSI target state machine is placed in 
38                                 the user space, while in SCST all the processing done in the kernel. Such architecture as STGT has was acknowledged
39                                 at the moment by the Linux SCSI subsystem maintainers as a "right" one, so kernel's part of STGT quickly
40                                 found its way to the kernel.</p>
41
42                                 <p>But such architecture has several inherent problems. Among them performance and complexity.
43                                 See description for the set of patches, submitted for the first iteration of in-kernel inclusion review and comments
44                                 <a href="http://lkml.org/lkml/2008/12/10/245">http://lkml.org/lkml/2008/12/10/245</a></p>
45                                 
46                                 <p>See also the following important discussions:
47                                 <ul>
48                                 
49                                 <li><span><a href="http://news.gmane.org/find-root.php?message_id=%3ce2e108260801170127w2937b2afg9bef324efa945e43%40mail.gmail.com%3e">
50                                 "Performance of SCST versus STGT"</a> for performance comparison.</span></li>
51                                 
52                                 <li><span><a href="http://news.gmane.org/find-root.php?message_id=%3c463F36AC.3010207%40vlnb.net%3e">
53                                 "Question for pass-through target design"</a></span></li>                               
54                                 
55                                 <li><span><a href="http://news.gmane.org/find-root.php?message_id=%3c43987F75.2000301%40vlnb.net%3e">
56                                 "Stgt a new version of iscsi target?"</a>, especially pay attention to 
57                                 this message: <a href="http://article.gmane.org/gmane.linux.scsi/21073">
58                                 http://article.gmane.org/gmane.linux.scsi/21073</a> for motivation why STGT's architecture was considered "right".
59                                 </span></li>
60                                 
61                                 <li><span>Thread
62                                 <a href="http://sourceforge.net/mailarchive/forum.php?thread_name=472F7FA4.7040303%40wpkg.org&forum_name=scst-devel">
63                                 "Relationship between SCST and in-kernel SCSI_TGT"</a>
64                                 </span></li>
65                                 
66                                 <li><span><a href="http://thread.gmane.org/gmane.linux.scsi/36417/focus=37273">this</a>
67                                 message in thread "Open-FCoE on linux-scsi" for more details.</span></li>
68                                 
69                                 </ul></p>
70                                 
71                                 <p>Also you shouldn't be deceived by the fact that some (small) part of STGT was accepted into the kernel.<br> 
72                                 It doesn't mean that STGT has the <strong>"kernel quality"</strong>. In fact, STGT as a whole similarly to any other
73                                 out-of-tree project lives on its own, hence has its own quality level, which isn't necessary better, than the 
74                                 quality level of SCST. Actually, from such important aspect of quality as simplicity, it 
75                                 might be quite contrary: e.g. SCST isn't required to support HIGHMEM (nowadays it 
76                                 isn't necessary, but required for all in-kernel components), which allowed to simplify memory management a lot.</p>     \r
77
78                                 <p>Interesting, on 2008 Linux Storage & Filesystem Workshop, namely in
79                                 <a href="http://www.usenix.org/event/lsf08/tech/lsf08sums.pdf">"Storage Track"</a> and
80                                 <a href="http://www.usenix.org/event/lsf08/tech/IO_bellinger.pdf">"Linux/iSCSI and a Generic Target Mode Storage
81                                 Engine for Linux v2.6"</a> documents, a special emphasis was put on the fact that SCST has "older" design,
82                                 while STGT has the "current" design. Well, this seems to be a good sign, because SCST opponents have come to so
83                                 little to say against it, so they started to use psychological arguments, exploiting the fact that most people
84                                 think that "newer" is always better.</p>
85
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93                         &copy; Copyright 2008 <b><font color="#EC981F">Vladislav Bolkhovitin & others.</font>&nbsp;&nbsp;\r
94                         Design by: <b><font color="#EC981F">Daniel Fernandes</font></b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;         \r
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