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git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@123 d57e44dd-8a1f-0410-8b47-8ef2f437770f
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Vladislav Bolkhovitin
2007-06-01 11:11:19 +00:00
parent 053ed51a93
commit 78b0dce0c2
2 changed files with 49 additions and 24 deletions
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scst/README
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@@ -342,7 +342,7 @@ subdirectories "vdisk" and "vcdrom". They have similar layout:
will go from the initiator.
- BLOCKIO - enables block mode, which will perform direct block
IO with the device, bypassing page-cache for all operations.
IO with a block device, bypassing page-cache for all operations.
This mode works ideally with high-end storage HBAs and for
applications that either do not need caching between application
and disk or need the large block throughput. See also below.

71
www/scst_page.html
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@@ -54,16 +54,20 @@ with different access permissions. For instance, initiator A could see
exported from
target T devices Da and Db read-writable, and initiator B from the same
target T could see devices Db read-only and Dc read-writable.<br>
</li>
<li> Complete SMP support.<br>
</li>
<li> Emulates necessary functionality of SCSI host adapter, because
from a remote initiator's point of view SCST acts as a SCSI host with
from remote initiators point of view SCST acts as a SCSI host with
its
own devices. Some of the emulated functions are the following:
own devices. This is especially important in pass-through mode with one
to many relationship, i.e. when
multiple initiators can connect to the exported pass-through devices.
You can find more deep elaboration why it is needed in&nbsp;<a
href="http://www.mail-archive.com/linux-scsi@vger.kernel.org/msg06911.html">this</a>
message in linux-scsi mailing list. Some of the emulated functions are
the following:
<ul>
<li> Generation of necessary UNIT ATTENTIONs, their storage and
delivery to all connected remote initiators (sessions). </li>
delivery to all connected remote initiators. </li>
<li> RESERVE/RELEASE functionality. </li>
<li> CA/ACA conditions (not implemented yet). </li>
<li> All types of RESETs and other task management functions. </li>
@@ -86,23 +90,24 @@ conditions treatment, data caching or passing commands in the user
space for device emulation. Example of such plugin is FILEIO device
handler (see below) .<br>
</li>
<li> Complete SMP support.<br>
</li>
<li> </li>
<li>Well documented.<br>
</li>
</ul>
<div style="text-align: justify;">
</div>
<p style="text-align: justify;">Interoperability between SCST and local
SCSI initiators (like sd, st) is
SCSI initiators (i.e. sd, st, etc.) is
the additional issue that SCST is going to address (it is not
implemented yet). It is necessary, because local SCSI initiators can
change the state of the device, for example RESERVE the device, or some
of its parameters and that would be done behind SCST, which could lead
to various problems. Thus, RESERVE/RELEASE commands, locally generated
of its parameters and that could be done behind SCST, which could lead
to various problems, including data corruption. Thus, RESERVE/RELEASE
commands, locally generated
UNIT ATTENTIONs, etc. should be intercepted and processed as if local
SCSI initiators act as remote SCSI initiators connected to SCST. This
feature requires some the kernel modification. Since in the current
version it is not implemented, SCST and target drivers are
able to work with any version of Linux 2.6 kernel.<br>
SCSI initiators act as remote SCSI initiators connected to SCST.<br>
</p>
<p style="text-align: justify;">Interface between SCST and target
drivers is based on work, done by <a href="http://www.iol.unh.edu/">University
@@ -111,26 +116,44 @@ of New Hampshire Interoperability Labs (UNH IOL)</a> for the <a
project</a>, which is currently developed on <a
href="http://unh-iscsi.sourceforge.net/">SourceForge.net</a>.<br>
</p>
<p style="text-align: justify;">The latest stable version is 0.9.5. It
supports SCSI disks (type 0), tapes (type 1), processors (type
<p style="text-align: justify;">SCST supports the following I/O modes:<br>
</p>
<ul>
<li>Pass-through mode with one to many relationship, i.e. when
multiple initiators can connect to the exported pass-through devices,
for virtually all SCSI devices types: disks
(type 0), tapes (type 1), processors (type
3), CDROMs (type 5), MO disks (type 7), medium changers (type 8) and
RAID controllers (type 0xC). Also it supports FILEIO and "performance"
device handlers. FILEIO device handler allows to use files on file
RAID controllers (type 0xC)</li>
<li>FILEIO mode, which allows to use files on file
systems or block devices as virtual remotely available SCSI disks or
CDROMs. "Performance" device handlers provide a way for direct
CDROMs with benefits of the Linux page cache<br>
</li>
<li>BLOCKIO mode, which performs direct block IO with a block device,
bypassing page-cache for all operations. This mode works ideally with
high-end storage HBAs and for applications that either do not need
caching between application and disk or need the large block throughput.</li>
<li>User space mode using scst_user device handler, which allows to
implement in the user space virtual SCSI devices in the SCST environment<br>
</li>
<li>"Performance" device handlers, which provide in pseudo
pass-through mode a way for direct
performance measurements without overhead of actual data transferring
from/to underlying SCSI device. Requires Linux kernel 2.6.14 or higher.
from/to underlying SCSI device<br>
</li>
</ul>
<p style="text-align: justify;">The latest stable version is 0.9.5.
Requires Linux kernel 2.6.14 or higher.
Tested mostly on i386 and x86_64,
but should also
work on any other
supported by Linux platform. More detail information you could find in
the project's README file.<br>
the project's README file.
</p>
Starting from version 0.9.4 2.4 Linux
kernels are not supported anymore, although there could be new SCST
releases for those kernels with very important bug fixes. The latest
kernels are not supported anymore. The latest
stable
version of SCST with 2.4 kernels support is 0.9.3.1-24.
version of SCST for 2.4 kernels is 0.9.3.1-24.
<p style="text-align: justify;">If you have any questions you can ask
them on the SCST SF.net page either using forum, or scst-devel mailing
list.<br>
@@ -140,7 +163,8 @@ list.<br>
page</a><br>
<a href="ChangeLog.scst">Change Log</a><br>
Documentation: <a href="doc/scst_pg.html">HTML</a>, <a
href="doc/scst_pg.pdf">PDF</a><br>
href="doc/scst_pg.pdf">PDF</a>, <a href="doc/scst_user_spec.txt">scst_user
interface description</a><br>
Some nice SCST call graphs, created by Ming Zhang: <a
href="doc/init_scst.png">init_scst</a>, <a
href="doc/scst_cmd_thread.png">scst_cmd_thread</a>, <a
@@ -151,6 +175,7 @@ available directly from the
project's SVN. The SCST release policy is to make stable releases
twice a year, with the only exception if the current stable version
contains a critical bug. Therefore on practice the development version
in the SVN
is usually more stable, than the "stable" one. You can access it using
either <a href="http://svn.sourceforge.net/scst">web-based SVN
repository viewer</a> or using anonymous access: </p>