linux/Documentation/scsi/osst.txt
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   1README file for the osst driver
   2===============================
   3(w) Kurt Garloff <garloff@suse.de> 12/2000
   4
   5This file describes the osst driver as of version 0.8.x/0.9.x, the released
   6version of the osst driver.
   7It is intended to help advanced users to understand the role of osst and to
   8get them started using (and maybe debugging) it.
   9It won't address issues like "How do I compile a kernel?" or "How do I load
  10a module?", as these are too basic.
  11Once the OnStream got merged into the official kernel, the distro makers
  12will provide the OnStream support for those who are not familiar with
  13hacking their kernels.
  14
  15
  16Purpose
  17-------
  18The osst driver was developed, because the standard SCSI tape driver in
  19Linux, st, does not support the OnStream SC-x0 SCSI tape. The st is not to
  20blame for that, as the OnStream tape drives do not support the standard SCSI
  21command set for Serial Access Storage Devices (SASDs), which basically
  22corresponds to the QIC-157 spec.
  23Nevertheless, the OnStream tapes are nice pieces of hardware and therefore
  24the osst driver has been written to make these tape devs supported by Linux.
  25The driver is free software. It's released under the GNU GPL and planned to
  26be integrated into the mainstream kernel.
  27
  28
  29Implementation
  30--------------
  31The osst is a new high-level SCSI driver, just like st, sr, sd and sg. It
  32can be compiled into the kernel or loaded as a module.
  33As it represents a new device, it got assigned a new device node: /dev/osstX
  34are character devices with major no 206 and minor numbers like the /dev/stX
  35devices. If those are not present, you may create them by calling
  36Makedevs.sh as root (see below).
  37The driver started being a copy of st and as such, the osst devices'
  38behavior looks very much the same as st to the userspace applications.
  39
  40
  41History
  42-------
  43In the first place, osst shared its identity very much with st. That meant
  44that it used the same kernel structures and the same device node as st.
  45So you could only have either of them being present in the kernel. This has
  46been fixed by registering an own device, now.
  47st and osst can coexist, each only accessing the devices it can support by
  48themselves.
  49
  50
  51Installation
  52------------
  53osst got integrated into the linux kernel. Select it during kernel
  54configuration as module or compile statically into the kernel.
  55Compile your kernel and install the modules.
  56
  57Now, your osst driver is inside the kernel or available as a module,
  58depending on your choice during kernel config. You may still need to create
  59the device nodes by calling the Makedevs.sh script (see below) manually.
  60
  61To load your module, you may use the command 
  62modprobe osst
  63as root. dmesg should show you, whether your OnStream tapes have been
  64recognized.
  65
  66If you want to have the module autoloaded on access to /dev/osst, you may
  67add something like
  68alias char-major-206 osst
  69to a file under /etc/modprobe.d/ directory.
  70
  71You may find it convenient to create a symbolic link 
  72ln -s nosst0 /dev/tape
  73to make programs assuming a default name of /dev/tape more convenient to
  74use.
  75
  76The device nodes for osst have to be created. Use the Makedevs.sh script
  77attached to this file.
  78
  79
  80Using it
  81--------
  82You may use the OnStream tape driver with your standard backup software,
  83which may be tar, cpio, amanda, arkeia, BRU, Lone Tar, ...
  84by specifying /dev/(n)osst0 as the tape device to use or using the above
  85symlink trick. The IOCTLs to control tape operation are also mostly
  86supported and you may try the mt (or mt_st) program to jump between
  87filemarks, eject the tape, ...
  88
  89There's one limitation: You need to use a block size of 32kB.
  90
  91(This limitation is worked on and will be fixed in version 0.8.8 of
  92 this driver.)
  93
  94If you just want to get started with standard software, here is an example
  95for creating and restoring a full backup:
  96# Backup
  97tar cvf - / --exclude /proc | buffer -s 32k -m 24M -B -t -o /dev/nosst0
  98# Restore
  99buffer -s 32k -m 8M -B -t -i /dev/osst0 | tar xvf - -C /
 100
 101The buffer command has been used to buffer the data before it goes to the
 102tape (or the file system) in order to smooth out the data stream and prevent
 103the tape from needing to stop and rewind. The OnStream does have an internal
 104buffer and a variable speed which help this, but especially on writing, the
 105buffering still proves useful in most cases. It also pads the data to
 106guarantees the block size of 32k. (Otherwise you may pass the -b64 option to
 107tar.)
 108Expect something like 1.8MB/s for the SC-x0 drives and 0.9MB/s for the DI-30.
 109The USB drive will give you about 0.7MB/s.
 110On a fast machine, you may profit from software data compression (z flag for
 111tar).
 112
 113
 114USB and IDE
 115-----------
 116Via the SCSI emulation layers usb-storage and ide-scsi, you can also use the
 117osst driver to drive the USB-30 and the DI-30 drives. (Unfortunately, there
 118is no such layer for the parallel port, otherwise the DP-30 would work as
 119well.) For the USB support, you need the latest 2.4.0-test kernels and the 
 120latest usb-storage driver from 
 121http://www.linux-usb.org/
 122http://sourceforge.net/cvs/?group_id=3581
 123
 124Note that the ide-tape driver as of 1.16f uses a slightly outdated on-tape
 125format and therefore is not completely interoperable with osst tapes.
 126
 127The ADR-x0 line is fully SCSI-2 compliant and is supported by st, not osst.
 128The on-tape format is supposed to be compatible with the one used by osst.
 129
 130
 131Feedback and updates
 132--------------------
 133The driver development is coordinated through a mailing list
 134<osst@linux1.onstream.nl>
 135a CVS repository and some web pages. 
 136The tester's pages which contain recent news and updated drivers to download
 137can be found on
 138http://sourceforge.net/projects/osst/
 139
 140If you find any problems, please have a look at the tester's page in order
 141to see whether the problem is already known and solved. Otherwise, please
 142report it to the mailing list. Your feedback is welcome. (This holds also
 143for reports of successful usage, of course.) 
 144In case of trouble, please do always provide the following info:
 145* driver and kernel version used (see syslog)
 146* driver messages (syslog)
 147* SCSI config and OnStream Firmware (/proc/scsi/scsi)
 148* description of error. Is it reproducible?
 149* software and commands used
 150
 151You may subscribe to the mailing list, BTW, it's a majordomo list.
 152
 153
 154Status
 155------
 1560.8.0 was the first widespread BETA release. Since then a lot of reports
 157have been sent, but mostly reported success or only minor trouble.
 158All the issues have been addressed.
 159Check the web pages for more info about the current developments.
 1600.9.x is the tree for the 2.3/2.4 kernel.
 161
 162
 163Acknowledgments
 164----------------
 165The driver has been started by making a copy of Kai Makisara's st driver.
 166Most of the development has been done by Willem Riede. The presence of the
 167userspace program osg (onstreamsg) from Terry Hardie has been rather
 168helpful. The same holds for Gadi Oxman's ide-tape support for the DI-30.
 169I did add some patches to those drivers as well and coordinated things a
 170little bit. 
 171Note that most of them did mostly spend their spare time for the creation of
 172this driver.
 173The people from OnStream, especially Jack Bombeeck did support this project
 174and always tried to answer HW or FW related questions. Furthermore, he
 175pushed the FW developers to do the right things.
 176SuSE did support this project by allowing me to work on it during my working
 177time for them and by integrating the driver into their distro.
 178
 179More people did help by sending useful comments. Sorry to those who have
 180been forgotten. Thanks to all the GNU/FSF and Linux developers who made this
 181platform such an interesting, nice and stable platform.
 182Thanks go to those who tested the drivers and did send useful reports. Your
 183help is needed!
 184
 185
 186Makedevs.sh
 187-----------
 188#!/bin/sh
 189# Script to create OnStream SC-x0 device nodes (major 206)
 190# Usage: Makedevs.sh [nos [path to dev]]
 191# $Id: README.osst.kernel,v 1.4 2000/12/20 14:13:15 garloff Exp $
 192major=206
 193nrs=4
 194dir=/dev
 195test -z "$1" || nrs=$1
 196test -z "$2" || dir=$2
 197declare -i nr
 198nr=0
 199test -d $dir || mkdir -p $dir
 200while test $nr -lt $nrs; do
 201  mknod $dir/osst$nr c $major $nr
 202  chown 0.disk $dir/osst$nr; chmod 660 $dir/osst$nr;
 203  mknod $dir/nosst$nr c $major $[nr+128]
 204  chown 0.disk $dir/nosst$nr; chmod 660 $dir/nosst$nr;
 205  mknod $dir/osst${nr}l c $major $[nr+32]
 206  chown 0.disk $dir/osst${nr}l; chmod 660 $dir/osst${nr}l;
 207  mknod $dir/nosst${nr}l c $major $[nr+160]
 208  chown 0.disk $dir/nosst${nr}l; chmod 660 $dir/nosst${nr}l;
 209  mknod $dir/osst${nr}m c $major $[nr+64]
 210  chown 0.disk $dir/osst${nr}m; chmod 660 $dir/osst${nr}m;
 211  mknod $dir/nosst${nr}m c $major $[nr+192]
 212  chown 0.disk $dir/nosst${nr}m; chmod 660 $dir/nosst${nr}m;
 213  mknod $dir/osst${nr}a c $major $[nr+96]
 214  chown 0.disk $dir/osst${nr}a; chmod 660 $dir/osst${nr}a;
 215  mknod $dir/nosst${nr}a c $major $[nr+224]
 216  chown 0.disk $dir/nosst${nr}a; chmod 660 $dir/nosst${nr}a;
 217  let nr+=1
 218done
 219
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