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diff --git a/Documentation/scsi/osst.txt b/Documentation/scsi/osst.txt new file mode 100644 index 000000000000..ce574e7791ab --- /dev/null +++ b/Documentation/scsi/osst.txt @@ -0,0 +1,219 @@ +README file for the osst driver +=============================== +(w) Kurt Garloff <garloff@suse.de> 12/2000 + +This file describes the osst driver as of version 0.8.x/0.9.x, the released +version of the osst driver. +It is intended to help advanced users to understand the role of osst and to +get them started using (and maybe debugging) it. +It won't address issues like "How do I compile a kernel?" or "How do I load +a module?", as these are too basic. +Once the OnStream got merged into the official kernel, the distro makers +will provide the OnStream support for those who are not familiar with +hacking their kernels. + + +Purpose +------- +The osst driver was developed, because the standard SCSI tape driver in +Linux, st, does not support the OnStream SC-x0 SCSI tape. The st is not to +blame for that, as the OnStream tape drives do not support the standard SCSI +command set for Serial Access Storage Devices (SASDs), which basically +corresponds to the QIC-157 spec. +Nevertheless, the OnStream tapes are nice pieces of hardware and therefore +the osst driver has been written to make these tape devs supported by Linux. +The driver is free software. It's released under the GNU GPL and planned to +be integrated into the mainstream kernel. + + +Implementation +-------------- +The osst is a new high-level SCSI driver, just like st, sr, sd and sg. It +can be compiled into the kernel or loaded as a module. +As it represents a new device, it got assigned a new device node: /dev/osstX +are character devices with major no 206 and minor numbers like the /dev/stX +devices. If those are not present, you may create them by calling +Makedevs.sh as root (see below). +The driver started being a copy of st and as such, the osst devices' +behavior looks very much the same as st to the userspace applications. + + +History +------- +In the first place, osst shared it's identity very much with st. That meant +that it used the same kernel structures and the same device node as st. +So you could only have either of them being present in the kernel. This has +been fixed by registering an own device, now. +st and osst can coexist, each only accessing the devices it can support by +themselves. + + +Installation +------------ +osst got integrated into the linux kernel. Select it during kernel +configuration as module or compile statically into the kernel. +Compile your kernel and install the modules. + +Now, your osst driver is inside the kernel or available as a module, +depending on your choice during kernel config. You may still need to create +the device nodes by calling the Makedevs.sh script (see below) manually, +unless you use a devfs kernel, where this won't be needed. + +To load your module, you may use the command +modprobe osst +as root. dmesg should show you, whether your OnStream tapes have been +recognized. + +If you want to have the module autoloaded on access to /dev/osst, you may +add something like +alias char-major-206 osst +to your /etc/modprobe.conf (before 2.6: modules.conf). + +You may find it convenient to create a symbolic link +ln -s nosst0 /dev/tape +to make programs assuming a default name of /dev/tape more convenient to +use. + +The device nodes for osst have to be created. Use the Makedevs.sh script +attached to this file. + + +Using it +-------- +You may use the OnStream tape driver with your standard backup software, +which may be tar, cpio, amanda, arkeia, BRU, Lone Tar, ... +by specifying /dev/(n)osst0 as the tape device to use or using the above +symlink trick. The IOCTLs to control tape operation are also mostly +supported and you may try the mt (or mt_st) program to jump between +filemarks, eject the tape, ... + +There's one limitation: You need to use a block size of 32kB. + +(This limitation is worked on and will be fixed in version 0.8.8 of + this driver.) + +If you just want to get started with standard software, here is an example +for creating and restoring a full backup: +# Backup +tar cvf - / --exclude /proc | buffer -s 32k -m 24M -B -t -o /dev/nosst0 +# Restore +buffer -s 32k -m 8M -B -t -i /dev/osst0 | tar xvf - -C / + +The buffer command has been used to buffer the data before it goes to the +tape (or the file system) in order to smooth out the data stream and prevent +the tape from needing to stop and rewind. The OnStream does have an internal +buffer and a variable speed which help this, but especially on writing, the +buffering still proves useful in most cases. It also pads the data to +guarantees the block size of 32k. (Otherwise you may pass the -b64 option to +tar.) +Expect something like 1.8MB/s for the SC-x0 drives and 0.9MB/s for the DI-30. +The USB drive will give you about 0.7MB/s. +On a fast machine, you may profit from software data compression (z flag for +tar). + + +USB and IDE +----------- +Via the SCSI emulation layers usb-storage and ide-scsi, you can also use the +osst driver to drive the USB-30 and the DI-30 drives. (Unfortunately, there +is no such layer for the parallel port, otherwise the DP-30 would work as +well.) For the USB support, you need the latest 2.4.0-test kernels and the +latest usb-storage driver from +http://www.linux-usb.org/ +http://sourceforge.net/cvs/?group_id=3581 + +Note that the ide-tape driver as of 1.16f uses a slightly outdated on-tape +format and therefore is not completely interoperable with osst tapes. + +The ADR-x0 line is fully SCSI-2 compliant and is supported by st, not osst. +The on-tape format is supposed to be compatible with the one used by osst. + + +Feedback and updates +-------------------- +The driver development is coordinated through a mailing list +<osst@linux1.onstream.nl> +a CVS repository and some web pages. +The tester's pages which contain recent news and updated drivers to download +can be found on +http://linux1.onstream.nl/test/ + +If you find any problems, please have a look at the tester's page in order +to see whether the problem is already known and solved. Otherwise, please +report it to the mailing list. Your feedback is welcome. (This holds also +for reports of successful usage, of course.) +In case of trouble, please do always provide the following info: +* driver and kernel version used (see syslog) +* driver messages (syslog) +* SCSI config and OnStream Firmware (/proc/scsi/scsi) +* description of error. Is it reproducible? +* software and commands used + +You may subscribe to the mailing list, BTW, it's a majordomo list. + + +Status +------ +0.8.0 was the first widespread BETA release. Since then a lot of reports +have been sent, but mostly reported success or only minor trouble. +All the issues have been addressed. +Check the web pages for more info about the current developments. +0.9.x is the tree for the 2.3/2.4 kernel. + + +Acknowledgments +---------------- +The driver has been started by making a copy of Kai Makisara's st driver. +Most of the development has been done by Willem Riede. The presence of the +userspace program osg (onstreamsg) from Terry Hardie has been rather +helpful. The same holds for Gadi Oxman's ide-tape support for the DI-30. +I did add some patches to those drivers as well and coordinated things a +little bit. +Note that most of them did mostly spend their spare time for the creation of +this driver. +The people from OnStream, especially Jack Bombeeck did support this project +and always tried to answer HW or FW related questions. Furthermore, he +pushed the FW developers to do the right things. +SuSE did support this project by allowing me to work on it during my working +time for them and by integrating the driver into their distro. + +More people did help by sending useful comments. Sorry to those who have +been forgotten. Thanks to all the GNU/FSF and Linux developers who made this +platform such an interesting, nice and stable platform. +Thanks go to those who tested the drivers and did send useful reports. Your +help is needed! + + +Makedevs.sh +----------- +#!/bin/sh +# Script to create OnStream SC-x0 device nodes (major 206) +# Usage: Makedevs.sh [nos [path to dev]] +# $Id: README.osst.kernel,v 1.4 2000/12/20 14:13:15 garloff Exp $ +major=206 +nrs=4 +dir=/dev +test -z "$1" || nrs=$1 +test -z "$2" || dir=$2 +declare -i nr +nr=0 +test -d $dir || mkdir -p $dir +while test $nr -lt $nrs; do + mknod $dir/osst$nr c $major $nr + chown 0.disk $dir/osst$nr; chmod 660 $dir/osst$nr; + mknod $dir/nosst$nr c $major $[nr+128] + chown 0.disk $dir/nosst$nr; chmod 660 $dir/nosst$nr; + mknod $dir/osst${nr}l c $major $[nr+32] + chown 0.disk $dir/osst${nr}l; chmod 660 $dir/osst${nr}l; + mknod $dir/nosst${nr}l c $major $[nr+160] + chown 0.disk $dir/nosst${nr}l; chmod 660 $dir/nosst${nr}l; + mknod $dir/osst${nr}m c $major $[nr+64] + chown 0.disk $dir/osst${nr}m; chmod 660 $dir/osst${nr}m; + mknod $dir/nosst${nr}m c $major $[nr+192] + chown 0.disk $dir/nosst${nr}m; chmod 660 $dir/nosst${nr}m; + mknod $dir/osst${nr}a c $major $[nr+96] + chown 0.disk $dir/osst${nr}a; chmod 660 $dir/osst${nr}a; + mknod $dir/nosst${nr}a c $major $[nr+224] + chown 0.disk $dir/nosst${nr}a; chmod 660 $dir/nosst${nr}a; + let nr+=1 +done |
