Intro ===== This file describes some issues involved when using the "ftape" floppy tape device driver that comes with the Linux kernel. This document deals with ftape-3.04 and later. Please read the section "Changes" for the most striking differences between version 3.04 and 2.08; the latter was the version of ftape delivered with the kernel until kernel version 2.0.30 and 2.1.57. ftape-3.x developed as the re-unification of ftape-2.x and zftape. zftape was developed in parallel with the stock ftape-2.x driver sharing the same hardware support but providing an enhanced file system interface. zftape also provided user transparent block-wise on-the-fly compression (regard it as a feature or bug of zftape). ftape has a home page at http://www.instmath.rwth-aachen.de/~heine/ftape/ which contains further information about ftape. Please cross check this WWW address against the address given (if any) in the MAINTAINERS file located in the top level directory of the Linux kernel source tree. Contents ======== A minus 1: Ftape documentation A. Changes 1. Goal 2. I/O Block Size 3. Write Access when not at EOD (End Of Data) or BOT (Begin Of Tape) 4. MTBSF - backspace over file mark and position at its EOT side 5. Formatting 6. Interchanging cartridges with other operating systems B. Debugging Output 1. Introduction 2. Tuning the debugging output C. Boot and load time configuration 1. Setting boot time parameters 2. Module load time parameters 3. Ftape boot- and load time options 4. Example kernel parameter setting 5. Example module parameter setting D. Support and contacts ******************************************************************************* A minus 1. Ftape documentation ============================== Unluckily, the ftape-HOWTO is out of date. This really needs to be changed. Up to date documentation as well as recent development versions of ftape and useful links to related topics can be found at the ftape home page at http://www.instmath.rwth-aachen.de/~heine/ftape/ ******************************************************************************* A. Changes ========== 1. Goal ~~~~ The goal of all that incompatibilities was to give ftape an interface that resembles the interface provided by SCSI tape drives as close as possible. Thus any Unix backup program that is known to work with SCSI tape drives should also work with ftape-3.04 and above. The concept of a fixed block size for read/write transfers is rather unrelated to this SCSI tape compatibility at the file system interface level. It developed out of a feature of zftape, a block wise user transparent on-the-fly compression. That compression support will not be dropped in future releases for compatibility reasons with previous releases of zftape. 2. I/O Block Size ~~~~~~~~~~~~~~ The probably most striking difference between ftape-2.x and ftape-3.x with the zftape file system interface is the concept of a fixed block size: data must be written to or read from the tape in multiples of a fixed block size. The block size defaults to 10k which is the default block size of GNU tar. While this is quite usual for SCSI tapes (block size of 32k?) and the QIC-150 driver `./drivers/char/tpqic02.c' ftape-2.x allowed data to be written in arbitrary portions to the tape. The block size can be tuned either during kernel configuration or at runtime with the MTIOCTOP ioctl using the MTSETBLK operation (i.e. do "mt -f /dev/qft0" setblk #BLKSZ). A block size of 0 switches to variable block size mode i.e. "mt setblk 0" switches off the block size restriction. However, this disables zftape's built in on-the-fly compression which doesn't work with variable block size mode. The BLKSZ parameter must be given as a byte count and must be a multiple of 32k or 0, i.e. use "mt setblk 32768" to switch to a block size of 32k. The typical symptom of a block size mismatch is an "invalid argument" error message. 3. Write Access when not at EOD (End Of Data) or BOT (Begin Of Tape) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ zftape (the file system interface of ftape-3.x) denies write access to the tape cartridge when it isn't positioned either at BOT or EOD. This inconvenience has been introduced as it was reported that the former behavior of ftape-2.x which allowed write access at arbitrary locations already has caused data loss with some backup programs. 4. MTBSF - backspace over file mark and position at its EOT side ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ftape-2.x didn't handle the MTBSF tape operation correctly. A MTBSF call (i.e. "mt -f /dev/nqft0 bsf #COUNT") should space over #COUNT file marks and then position at the EOT tape side of the file mark. This has to be taken literally, i.e. "mt -f /dev/nqft0 bsf 1" should simply position at the start of the current volume. 5. Formatting ~~~~~~~~~~ ftape-3.x DOES support formatting of floppy tape cartridges. You need the `ftformat' program that is shipped with the modules version of ftape-3.x. Please get the latest version of ftape from ftp://sunsite.unc.edu/pub/Linux/kernel/tapes or from the ftape home page at http://www.instmath.rwth-aachen.de/~heine/ftape/ `ftformat' is contained in the `./contrib/' subdirectory of that separate ftape package. 6. Interchanging cartridges with other operating systems ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The internal emulation of Unix tape device file marks has changed completely. ftape-3.x now uses the volume table segment as specified by the QIC-40/80/3010/3020/113 standards to emulate file marks. As a consequence there is limited support to interchange cartridges with other operating systems. To be more precise: ftape will detect volumes written by other OS's programs and other OS's programs will detect volumes written by ftape-3.x. However, it isn't possible to extract the data dumped to the tape by some MSDOG program with ftape-3.x. This exceeds the scope of a kernel device driver. If you need such functionality, then go ahead and write a user space utility that is able to do that. ftape-3.x/zftape already provides all kernel level support necessary to do that. ******************************************************************************* B. Debugging Output ================ 1. Introduction ~~~~~~~~~~~~ The ftape driver can be very noisy in that is can print lots of debugging messages to the kernel log files and the system console. While this is useful for debugging it might be annoying during normal use and enlarges the size of the driver by several kilobytes. To reduce the size of the driver you can trim the maximal amount of debugging information available during kernel configuration. Please refer to the kernel configuration script and its on-line help functionality. The amount of debugging output maps to the "tracing" boot time option and the "ft_tracing" modules option as follows: 0 bugs 1 + errors (with call-stack dump) 2 + warnings 3 + information 4 + more information 5 + program flow 6 + fdc/dma info 7 + data flow 8 + everything else 2. Tuning the debugging output ~~~~~~~~~~~~~~~~~~~~~~~~~~~ To reduce the amount of debugging output printed to the system console you can i) trim the debugging output at run-time with mt -f /dev/nqft0 setdensity #DBGLVL where "#DBGLVL" is a number between 0 and 9 ii) trim the debugging output at module load time with insmod ftape.o ft_tracing=#DBGLVL Of course, this applies only if you have configured ftape to be compiled as a module. iii) trim the debugging output during system boot time. Add the following to the kernel command line: ftape=#DBGLVL,tracing Please refer also to the next section if you don't know how to set boot time parameters. ******************************************************************************* C. Boot and load time configuration ================================ 1. Setting boot time parameters ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Assuming that you use lilo, the LI)nux LO)ader, boot time kernel parameters can be set by adding a line append some_kernel_boot_time_parameter to `/etc/lilo.conf' or at real boot time by typing in the options at the prompt provided by LILO. I can't give you advice on how to specify those parameters with other loaders as I don't use them. For ftape, each "some_kernel_boot_time_parameter" looks like "ftape=value,option". As an example, the debugging output can be increased with ftape=4,tracing NOTE: the value precedes the option name. 2. Module load time parameters ~~~~~~~~~~~~~~~~~~~~~~~~~~~ Module parameters can be specified either directly when invoking the program 'insmod' at the shell prompt: insmod ftape.o ft_tracing=4 or by editing the file `/etc/modules.conf' in which case they take effect each time when the module is loaded with `modprobe' (please refer to the modules documentation, i.e. `modules.txt' and the respective manual pages). Thus, you should add a line options ftape ft_tracing=4 to `/etc/modules.conf` if you intend to increase the debugging output of the driver. 3. Ftape boot- and load time options ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ i. Controlling the amount of debugging output DBGLVL has to be replaced by a number between 0 and 8. module | kernel command line -----------------------|---------------------- ft_tracing=DBGLVL | ftape=DBGLVL,tracing ii. Hardware setup BASE is the base address of your floppy disk controller, IRQ and DMA give its interrupt and DMA channel, respectively. BOOL is an integer, "0" means "no"; any other value means "yes". You don't need to specify anything if connecting your tape drive to the standard floppy disk controller. All of these values have reasonable defaults. The defaults can be modified during kernel configuration, i.e. while running "make config", "make menuconfig" or "make xconfig" in the top level directory of the Linux kernel source tree. Please refer also to the on line documentation provided during that kernel configuration process. module | kernel command line -----------------------|---------------------- ft_fdc_base=BASE | ftape=BASE,ioport ft_fdc_irq=IRQ | ftape=IRQ,irq ft_fdc_dma=DMA | ftape=DMA,dma ft_probe_fc10=BOOL | ftape=BOOL,fc10 ft_mach2=BOOL | ftape=BOOL,mach2 ft_fdc_threshold=THR | ftape=THR,threshold ft_fdc_rate_limit=RATE | ftape=RATE,datarate 4. Example kernel parameter setting ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ To configure ftape to probe for a Colorado FC-10/FC-20 controller and to increase the amount of debugging output a little bit, add the following line to `/etc/lilo.conf': append ftape=1,fc10 ftape=4,tracing 5. Example module parameter setting ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ To do the same, but with ftape compiled as a loadable kernel module, add the following line to `/etc/modules.conf': options ftape ft_probe_fc10=1 ft_tracing=4 ******************************************************************************* D. Support and contacts ==================== Ftape is distributed under the GNU General Public License. There is absolutely no warranty for this software. However, you can reach the current maintainer of the ftape package under the email address given in the MAINTAINERS file which is located in the top level directory of the Linux kernel source tree. There you'll find also the relevant mailing list to use as a discussion forum and the web page to query for the most recent documentation, related work and development versions of ftape. LocalWords: ftape Linux zftape http www rwth aachen LBFM claus EOD config LocalWords: datarate LocalWords BOT MTBSF EOT HOWTO QIC tpqic menuconfig LocalWords: MTIOCTOP MTSETBLK mt dev qft setblk BLKSZ bsf zftape's xconfig LocalWords: nqft ftformat ftp sunsite unc edu contrib ft MSDOG fdc LocalWords: dma setdensity DBGLVL insmod lilo LI nux ader conf txt LocalWords: modprobe IRQ BOOL ioport irq fc mach THR