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9. Frequently Asked Questions

This is a collection of questions that get asked once in a while, which could fall into the category of FAQ's. If you feel that there is some question that ought to be added to the list, please feel free to mail me (but do include an answer, thanks!).

9.1 Does ftape support the Iomega 2GB tape drive?

Sorry, no, it doesn't. Iomega uses a proprietary data format on their 'Ditto 2GB' tape cartridges. The maintainer of ftape has been unable to get the necessary information to include support from the vendor.

9.2 How fast is ftape?

You can achieve quite respectable backup and restore speeds with ftape: a Colorado DJ-20 and an Adaptec 1542CF controller, has been measured at 4.25Mbyte/min sustained data transfer rate (no compression) across a 70Mbyte tar archive, while comparing the archive on the tape with data on an IDE disk. The speed of ftape is mostly dependent on the data transfer rate of your FDC: The AHA1542CF has a ``post-1991 82077'' FDC, and it will push 1Mbit/sec at the tape drive. If you have an FDC which can only deliver 500Kbit/sec data rates, you will see half the transfer rate (well, roughly).

9.3 How do I change the trace-level?

There are three ways you can do this (in order of personal preference).

While we're at it, here are the meanings of the various trace levels.

Using insmod to change trace-level

If you are using the modules mechanism to load the ftape driver, you can specify the tracing level as an option to the insmod command.

        /sbin/insmod ftape.o tracing=<tracing-level>

Using mt to change trace-level

The ftape driver has a hack in it that allows the fsr option in mt to be used to set the tracing level. zftape does not have this hack.

        mt -f /dev/ftape fsr <tracing-level>

The use of the fsr command in mt is a hack, and will probably disappear or change with time.

Recompiling to change trace-level

The file tracing.c contains a line int tracing = 3;. Change the 3 to whatever is appropriate and recompile.

9.4 Can I exchange tapes with someone using DOS?

No. The DOS software conforms to the QIC-80 specs about the layout of the DOS filesystem, and it should(?) be a small problem to write a program that can read/write the DOS format. In fact, I'd bet that creating a nice user interface would be a bigger problem.

9.5 How do I `....' with tar?

These are really tar questions: Please read the man page and the info page. If you have not got it either, try `tar --help 2>&1 | less'.

If your version of tar is v1.11.1 or earlier, consider upgrading to v1.11.8 - This version can call GNU zip directly (i.e.: it supports the -z option) and has an elaborate help included. Also, it compiles right out of the box on Linux.

9.6 ftape DMA transfers gives ECC errors

Sadly to say there are some SVGA cards and Ethernet cards that do not decode their addresses correct. This typically happens when the ftape buffers are in the range 0x1a0000 to 0x1c0000. Somehow, the DMA write cycles get clobbered and every other byte written gets a bad value (0xff). These problems are reported to happen with both SVGA and Ethernet cards. We know of at least one (bad?) ATI 16bit VGA card that caused this.

The easiest solution is to put the card in an 8bit slot (it is often not enough to reconfigure the card to 8bit transfers). Moving the ftape buffer away from the VGA range is only a partial solution; All DMA buffers used in Linux can have this problem! Let us make this one clear: This has nothing to do with the ftape software.

9.7 insmod says the kernel version is wrong

The insmod program can check the kernel version against the version that ftape was compiled for in two ways: It can directly compare the kernel version number recorded in the ftape module against the version of the running kernel, or, if both the kernel and ftape is compiled with versioned symbols, compare the version of the used kernel symbols.

If you have upgraded your version of GCC to v2.7.0 or later, you must recompile the modules utilities with gcc v2.7.x.

Newer versions of insmod allows you to ``force'' insertion of a module into the kernel, even though the version string is incorrect.

9.8 What is this versioned symbols stuff anyway?

When you say `yes' to CONFIG_MODVERSIONS during `make config', all the symbols exported by the kernel, i.e: the symbols that the loadable modules can ``see'', are augmented to include a checksum across the types of the call/return parameters. This allows insmod to detect whether the definition of a variable or function in the kernel has changed since the time when ftape was compiled.

This ensures a high degree of safety, such that you do not crash the kernel because you used an outdated module with your kernel.

If you enable CONFIG_MODVERSIONS in the kernel, make sure you have `-DMODVERSIONS -include /usr/include/linux/modversions.h' uncommented in the MODULE_OPT line in the ftape Makefile. Conversely, if you do not have CONFIG_MODVERSIONS enabled, make sure you have it commented out.

9.9 insmod says that kernel 1.2.0 and 1.2.0 differ

Did you remember to apply the ksyms.c patch to the kernel? If not, read the README.linux-1.2 file in the source distribution.

9.10 ftape says ``This tape has no 'Linux raw format'''

You get this complaint if you haven't erased your freshly formatted tape. This is because ftape expect a ``magic header'' on the tape, to be able that it is allowed to interpret the header segment in its own way (eg: file marks). To remove the problem, say `mt -f /dev/nftape erase'

9.11 Where can I find the tar/mt/cpio/ddbinaries/sources/manpages?

All of these tools have been developed by the GNU project, and the source (and man page) can be fetched from just-about any ftp site in the world (including,, and In any case they can be fetched from the official GNU home site: []:/pub/gnu. The latest versions (as of September 12 1996) are:

        cpio:   2.4.2 (cpio-2.4.2.tar.gz)
        dd:     3.13 (fileutils-3.13.tar.gz)
        mt:     2.4.2 (cpio-2.4.2.tar.gz)
        tar:    1.11.8 (tar-1.11.8.tar.gz)
        gzip:   1.2.4 (gzip-1.2.4.tar.gz)

They all compile out of the box on Linux v1.0.4 / libc v4.5.19 / gcc v2.5.8.

9.12 Where can I obtain the QIC standards?

If you wish to help developing ftape, or add some utility (e.g. a tape formatting program), you will need that appropriate QIC standards. The standard(s) to get is: QIC-80, -117, -3010, and 3020. QIC-117 describes how commands are sent to the tape drive (including timing etc), so you would probably never need it. QIC-80/3010/3020 describes higher level part, such as tape layout, ECC code, standard filesystem. You can get the QIC standards from the following address:

Quarter Inch Cartridge Drive Standards, Inc.
311 East Carrillo Street
Santa Barbara, California 93101
Phone: (805) 963-3853
Fax:   (805) 962-1541

Note: They are registered as `Freeman Associates, Inc' in the phone book.

9.13 What block-size should I use with tar

When using compression, and in all general, it can be a benefit to specify to tar, that it should block the output into chunks. Since ftape cuts things into 29Kbyte blocks, saying `-b58' should be optimum.

``Why 29Kbyte?'', I hear you cry. Well, the QIC-80 standard specifies that all data should be protected by an Error Correcting Code (ECC) code. The code specified in the QIC-80 standard is known as a Reed-Solomon (R-S) code. The R-S code takes 29 data bytes and generates 3 parity bytes. To increase the performance of the ECC code, the parity bytes are generated across 29 1Kbyte sectors. Thus, ftape takes 29Kbytes of data, adds 3Kbytes of ECC parity, and writes 32Kbytes to the tape at a time. For this reason, ftape will always read and write 32K byte blocks to be able to detect (and correct) data errors.

If you are curious, and wish to know more, look in the ecc.c and ecc.h files, for an explanation of the code and a reference to a textbook on Reed-Solomon codes.

9.14 ftape detects more bad sectors than DOS on QIC-3020 tapes

If you look at the difference, you will notice that ftape always detects 2784 sectors more than DOS.

The number that ftape reports is correct (of course :-). Each correctly formatted QIC-3020 tape has 2784 sectors at fixed positions that are marked in the bad sector map. To quote from the specs:

``Tracks 5,7,9,11,13,15,17,19,21,23,25 and 27 within 4 segments of either EOT or BOT are prone to increased error rates due to hole imprints. Therefore, these regions shall be mapped as bad at format time and entered in the bad sector map by indicating that all sectors within the identified segments are bad.''

This gives 12 tracks * 2 * 4 segments * 29 sectors == 2784 sectors.

So ftape choose to report the real number of sectors that cannot be used on the tape, while DOS gives a more optimistic number giving a better indication of tape quality. (ftape's behavior might change in the future to detect correct formatting and display the separate numbers. It has rather low priority though).

QIC-3010 are alike QIC-3020 tapes regarding this.

9.15 Syslogd works overtime when running ftape

The compile-time options NO_TRACE and NO_TRACE_AT_ALL in ftape control the amount of system logging. Add whichever is appropriate to the FTAPE_OPT line in the Makefile and recompile.

9.16 `Shoeshining'

There been a few reports of `shoeshining'. This is when the tape just seems to run back and forth endlessly. This has been seen on a Jumbo 250 ( and on an Iomega 250 Ditto Insider ( In the latter case it has been narrowed own to using an ELF Linux and running off a SCSI hard disk (connected to an Adaptec 1542cf). Please contact me if you have an update to this problem.

9.17 Trying to compile ftape gives me the error`"modversions.h: no such file or directory'

The modversions.h file is created when the kernel is compiled with the configuration item CONFIG_MODVERSIONS turned on. With this option enabled, the file will be created during the make dep step.

One more handy tip is that a make mrproper will remove /usr/include/linux/modversions.h. You will need to reconfig the kernel and do a make dep to get the file back.

9.18 How does `mt eom' work when you've started overwriting a tapein the middle?

(EOM is "End Of recorded Media", the position right after all data already recorded to the tape)

One cannot use tape "files" like files on an ordinary file system.

In principle, a tape doesn't allow anything but appending new data at EOM. However, if one positiones just in the middle of the already recorded data AND starts writing, then the driver first deletes all following files (thus moving the EOM to the actual position) and then starts writing.

Thus, the new EOM after finishing the write process, is then after the newly recorded data.

One of the consequences of the above is, of course, that writing to the tape in the middle of the already recorded area, is destructive in the sense, that it not only overwrites the "file" the tape is positioned at, but also deletes all following files.

9.19 Help! I'm getting 'dmaalloc() failed' in my syslog file.

You should only see this is you are trying to insmod the ftape.o module. Try running swapout first. It is provided with the standalone ftape source. It doesn't appear in the ftape source that's provided with the kernel.

Here's an example of how you can set your rc.local file to use it.

        # Install the Floppy Tape Driver
        if [ -f /boot/modules/`uname -r`/misc/ftape.o ]; then
            echo Installing ftape for Linux `uname -r`
            insmod /boot/modules/`uname -r`/misc/ftape.o

Please note that you won't have this type of problem if you compile the ftape driver into the kernel.

9.20 Is it ok that I'm not hearing the tape move when I do a fsf or a bsf with mt?

Yes. The driver merely updates an internal counter when those commands are issues. The tape should move to the proper location on the next read or write access to the tape drive.

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