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/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 it's 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,
 60unless you use a devfs kernel, where this won't be needed.
 61
 62To load your module, you may use the command 
 63modprobe osst
 64as root. dmesg should show you, whether your OnStream tapes have been
 65recognized.
 66
 67If you want to have the module autoloaded on access to /dev/osst, you may
 68add something like
 69alias char-major-206 osst
 70to your /etc/modprobe.conf (before 2.6: modules.conf).
 71
 72You may find it convenient to create a symbolic link 
 73ln -s nosst0 /dev/tape
 74to make programs assuming a default name of /dev/tape more convenient to
 75use.
 76
 77The device nodes for osst have to be created. Use the Makedevs.sh script
 78attached to this file.
 79
 80
 81Using it
 82--------
 83You may use the OnStream tape driver with your standard backup software,
 84which may be tar, cpio, amanda, arkeia, BRU, Lone Tar, ...
 85by specifying /dev/(n)osst0 as the tape device to use or using the above
 86symlink trick. The IOCTLs to control tape operation are also mostly
 87supported and you may try the mt (or mt_st) program to jump between
 88filemarks, eject the tape, ...
 89
 90There's one limitation: You need to use a block size of 32kB.
 91
 92(This limitation is worked on and will be fixed in version 0.8.8 of
 93 this driver.)
 94
 95If you just want to get started with standard software, here is an example
 96for creating and restoring a full backup:
 97# Backup
 98tar cvf - / --exclude /proc | buffer -s 32k -m 24M -B -t -o /dev/nosst0
 99# Restore
100buffer -s 32k -m 8M -B -t -i /dev/osst0 | tar xvf - -C /
101
102The buffer command has been used to buffer the data before it goes to the
103tape (or the file system) in order to smooth out the data stream and prevent
104the tape from needing to stop and rewind. The OnStream does have an internal
105buffer and a variable speed which help this, but especially on writing, the
106buffering still proves useful in most cases. It also pads the data to
107guarantees the block size of 32k. (Otherwise you may pass the -b64 option to
108tar.)
109Expect something like 1.8MB/s for the SC-x0 drives and 0.9MB/s for the DI-30.
110The USB drive will give you about 0.7MB/s.
111On a fast machine, you may profit from software data compression (z flag for
112tar).
113
114
115USB and IDE
116-----------
117Via the SCSI emulation layers usb-storage and ide-scsi, you can also use the
118osst driver to drive the USB-30 and the DI-30 drives. (Unfortunately, there
119is no such layer for the parallel port, otherwise the DP-30 would work as
120well.) For the USB support, you need the latest 2.4.0-test kernels and the 
121latest usb-storage driver from 
122http://www.linux-usb.org/
123http://sourceforge.net/cvs/?group_id=3581
124
125Note that the ide-tape driver as of 1.16f uses a slightly outdated on-tape
126format and therefore is not completely interoperable with osst tapes.
127
128The ADR-x0 line is fully SCSI-2 compliant and is supported by st, not osst.
129The on-tape format is supposed to be compatible with the one used by osst.
130
131
132Feedback and updates
133--------------------
134The driver development is coordinated through a mailing list
135<osst@linux1.onstream.nl>
136a CVS repository and some web pages. 
137The tester's pages which contain recent news and updated drivers to download
138can be found on
139http://linux1.onstream.nl/test/
140
141If you find any problems, please have a look at the tester's page in order
142to see whether the problem is already known and solved. Otherwise, please
143report it to the mailing list. Your feedback is welcome. (This holds also
144for reports of successful usage, of course.) 
145In case of trouble, please do always provide the following info:
146* driver and kernel version used (see syslog)
147* driver messages (syslog)
148* SCSI config and OnStream Firmware (/proc/scsi/scsi)
149* description of error. Is it reproducible?
150* software and commands used
151
152You may subscribe to the mailing list, BTW, it's a majordomo list.
153
154
155Status
156------
1570.8.0 was the first widespread BETA release. Since then a lot of reports
158have been sent, but mostly reported success or only minor trouble.
159All the issues have been addressed.
160Check the web pages for more info about the current developments.
1610.9.x is the tree for the 2.3/2.4 kernel.
162
163
164Acknowledgments
165----------------
166The driver has been started by making a copy of Kai Makisara's st driver.
167Most of the development has been done by Willem Riede. The presence of the
168userspace program osg (onstreamsg) from Terry Hardie has been rather
169helpful. The same holds for Gadi Oxman's ide-tape support for the DI-30.
170I did add some patches to those drivers as well and coordinated things a
171little bit. 
172Note that most of them did mostly spend their spare time for the creation of
173this driver.
174The people from OnStream, especially Jack Bombeeck did support this project
175and always tried to answer HW or FW related questions. Furthermore, he
176pushed the FW developers to do the right things.
177SuSE did support this project by allowing me to work on it during my working
178time for them and by integrating the driver into their distro.
179
180More people did help by sending useful comments. Sorry to those who have
181been forgotten. Thanks to all the GNU/FSF and Linux developers who made this
182platform such an interesting, nice and stable platform.
183Thanks go to those who tested the drivers and did send useful reports. Your
184help is needed!
185
186
187Makedevs.sh
188-----------
189#!/bin/sh
190# Script to create OnStream SC-x0 device nodes (major 206)
191# Usage: Makedevs.sh [nos [path to dev]]
192# $Id: README.osst.kernel,v 1.4 2000/12/20 14:13:15 garloff Exp $
193major=206
194nrs=4
195dir=/dev
196test -z "$1" || nrs=$1
197test -z "$2" || dir=$2
198declare -i nr
199nr=0
200test -d $dir || mkdir -p $dir
201while test $nr -lt $nrs; do
202  mknod $dir/osst$nr c $major $nr
203  chown 0.disk $dir/osst$nr; chmod 660 $dir/osst$nr;
204  mknod $dir/nosst$nr c $major $[nr+128]
205  chown 0.disk $dir/nosst$nr; chmod 660 $dir/nosst$nr;
206  mknod $dir/osst${nr}l c $major $[nr+32]
207  chown 0.disk $dir/osst${nr}l; chmod 660 $dir/osst${nr}l;
208  mknod $dir/nosst${nr}l c $major $[nr+160]
209  chown 0.disk $dir/nosst${nr}l; chmod 660 $dir/nosst${nr}l;
210  mknod $dir/osst${nr}m c $major $[nr+64]
211  chown 0.disk $dir/osst${nr}m; chmod 660 $dir/osst${nr}m;
212  mknod $dir/nosst${nr}m c $major $[nr+192]
213  chown 0.disk $dir/nosst${nr}m; chmod 660 $dir/nosst${nr}m;
214  mknod $dir/osst${nr}a c $major $[nr+96]
215  chown 0.disk $dir/osst${nr}a; chmod 660 $dir/osst${nr}a;
216  mknod $dir/nosst${nr}a c $major $[nr+224]
217  chown 0.disk $dir/nosst${nr}a; chmod 660 $dir/nosst${nr}a;
218  let nr+=1
219done