root@krishna.info-gw.mese.com (Sarat Vemuri) writes:

quoted text
>The vulnarability of Un*x file systems to sudden powerdowns 
>convinced me to buy a tape drive to backup frequently
>(Now that I run my own Linux box).  But I don't know a
>thing about different standards of Tape drives out there.
>I do know that, most drives use proprietery software under
>DOS.  Compatiablity was never an issue under DOS. Now
>suddenly I realize that I need to enhance my knowledge of
>Tape drives and stadards.  So let me ask the following
>questions.
>
>1.  What are the different non SCSI standards available 
>    for interface with the computer?

The two major ones I know about are:

1.  Connect to and use the floppy disk controller.  This usually does more
    than just use it as a data path, it actually makes use of the controller
    functionality to run the tape drive.  I believe the standard for this is
    QIC-02 (I can't find my copy at the moment) and there are rumored to be
    a few that do not follow this standard.

    I personally would not try to use this means of connection.  Your mileage
    may vary.

2.  Connect to the parallel port.  This is difficult because the parallel
    port was intended for printing and is not a truly bidirectional interface
    and is reported to be unreliable in certain cases as well.  In order to
    accomplish bidirectionality and improved reliability, some sneaky designs
    have come up.  These may be using tricks like toggling available status
    lines and such to achieve a data flow.  The problem is that all this does
    take some level of work to develop and test, and the companies do not want
    to let their competitors see what they have done.  However with half a
    dozen such companies on the market, it seems moot to me, even if all the
    designs are different.

    I'd prefer some kind of connection that at least CAN be external, and
    the parallel port would be nice since it is about all you have besides
    the serial port for laptops.

    My tendency, given this situation, is to go with SCSI.  You can get
    more variety in backup software even for DOS this way.


quoted text
>2.  What are different recording format standards?

    QIC-40 and QIC-80 are formats that define the range from low level
    block definitions, to upper level file system representation.

    QIC-150 and QIC-525 define low level block definitions.  I didn't see
    and high level for QIC-525 but someone did tell me it had it (maybe we
    just didn't have a common understanding of what was low level and what
    was high level).

quoted text
>3.  What formats of interface is supported  by Linux?
>    I see that there are drivers for QIC-02 working and 
>    I understand that drivers for QIC-40/80 is under works.
>    But what are those numbers QIC thingies?

    QIC-02 is the interface via a floppy controller.  It would tell you
    what floppy disk operations to perform to do things on the tape.

    QIC-40/80 define a lot of things, from how many tracks on tape, which
    ones are data or sync, data transition timings required, syncronization
    and lead in patterns for blocks, the order of tracks on the tape (odd
    tracks forward, even tracks backward, for instance).  These things could
    or should be done by the tape control firmware.  This is not always the
    case.  It also defines how to lay out the filesystem on tape, such as
    where the file name goes, where the date and size of the file goes, how
    to write the data from the file, etc.  This is almost always done by
    the software.

    QIC-150 and QIC-525 define the low level stuff only.  On UNIX you should
    end up with a stream device in /dev to which you can output directly
    with your own programs.  You can use tar or cpio or make up whatever you
    want as a format.  You can compress the data before being written, too.


quoted text
>4.  I don't have any money to spend on SCSI, so please advise
>    me on what kind of non SCSI drive to buy.

    There is NO non-SCSI solution that is ideal.  You will have to detail
    your particular needs.  Well even SCSI is not ideal (until they make
    a SCSI interface standard on all laptops).

    I cannot currently recommend parallel port drives, and I would not
    recommend floppy disk controller drives.  I've heard there are tape
    drives for Ethernet, but this is likely to be at least as costly as
    SCSI.

    I'd recommend getting SCSI and a QIC-150 (using DC6250 tapes you get
    250 megabytes of basic capacity (500 megabytes if you data can be
    compressed to the 2:1 level)).  In the longer run this might be a
    better choice than QIC-40/80.  But if exchanging data with DOS machines
    is more important to you than exchanging with UNIX machines, then maybe
    some QIC-80 drive would be preferred (please disregard QIC-40).
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