.TH ft "" "" "Device Driver"
.PC "Floppy-tape driver"
.B /dev/ft
.PP
.II /dev/ft
.II "floppy tape^driver"
.II "tape, floppy^driver"
.II "driver^floppy tape"
.II "device driver^floppy tape"
The device driver
.B ft
supports floppy-tape drives.
It has major number 4.
Minor-number assignments are documented in the header file
.BR /usr/include/sys/ft.h .
.PP
.B ft
works with QIC-40 and QIC-80 drives from Colorado, Archive, Mountain,
and Summit.
It offers the following features:
.IP \(bu 0.3i
It uses the bad-block bitmap that is written into the first two 32-kilobyte
segments of tape at format time.
.IP \(bu
.II "Reed-Solomon error correction"
.II "error-correction code^Reed-Solomon"
It uses standard QIC-40/QIC-80 Reed-Solomon error-correcting code (ECC).
This technique uses three of every 32 blocks for error checking.
A tape block is one kilobyte long.
.IP \(bu
It supports no-rewind-on-close.
This feature permits you to concatenate several archives onto a single
tape cartridge.
.IP \(bu
It performs auto-configuration for users who do not know if their drives use
soft select A or soft select B, or hard select on unit 0, 1, 2, or 3,
with manual override.
.IP \(bu
It lets you configure the size of the tape buffer,
from 64 through 4,064 kilobytes.
.IP \(bu
It reads from and writes to buffer space rather than going to tape
whenever possible.
.IP \(bu
It works with partially formatted tapes.
Some formatting utilities let you select
the number of tape tracks to format, in case you do not want to take
the time to format an entire cartridge.
.IP \(bu
It recognizes both 205-foot and 307.5-foot tapes.
.IP \(bu
It works with the \*(CO command
.B tape
with the following arguments:
.BR rewind ,
.BR retension ,
.BR seek ,
.BR status ,
and
.BR tell .
.PP
Please note that release 1.0 of
.B ft
has the following limitations:
.IP \(bu 0.3i
It does not format tapes.
For now, we suggest that you buy pre-formatted tapes,
or use formatting utilities available under other operating systems.
.IP \(bu
It does not support the QIC-80 formats for \*(MD or \*(UU file systems
on tape.
These features do not need to be part of the device
driver, and can be implemented by user-level applications.
.IP \(bu
It does not perform data compression, as documented in QIC-122.
Other forms of data compression are presently available under \*(CO,
such as the
.B \-z
option supported by the tape-archive command
.BR gtar .
.IP \(bu
The device driver is character-only:
there is no corresponding block device for floppy tape.
.IP \(bu
It does not support 1,100-foot tapes.
Although the QIC-80 standard mentions this length, it is not in common use.
.IP \(bu
You cannot access a floppy-disk drive from \*(CO while a floppy-tape
drive is in use.
Likewise, if a floppy disk is in use \(em for
example, if it is mounted \(em you cannot access the floppy-tape drive.
.IP \(bu
Although a QIC-80 drive can read a tape that was formatted for QIC-40,
it cannot write to such a tape.
The cartridge must be reformatted for QIC-80
before a QIC-80 drive can write to it.
.SH "See Also"
.Xr "device drivers," device_dr
.Xr "fd," fd
.Xr "ftbad," ftbad
.Xr "gnucpio," gnucpio
.Xr "gtar," gtar
.Xr "tape" tape
.SH Notes
.B ft
reports any error that may affect integrity of the data.
If the same block number appears repeatedly in
.BR ft 's
warning messages,
it is a problem on the tape and the block should be in the bad block list.
Because the Reed-Solomon ECC used in
.B ft
allows the physical medium to spoil up to three of every 32
one-kilobyte blocks yet recover all data, your data set may still be
recoverable despite these errors;
but you should consider using the command
.B ftbad
to add such blocks to your cartridge's list of bad blocks
before you again write data onto that cartridge.
.PP
The message:
.DM
	Get Reference Burst Failed
.DE
.PP
can occur if you attempt to back up to an unformatted tape, or one who's
format is unrecognizable.
If a backup fails with this message, try using another, formatted cartridge.
.PP
Systems with a very slow CPU (e.g., a 16-megahertz 80386SX) may have
trouble running
.B ft
in multi-user mode.
The reason is that floppy-tape hardware does not have much intelligence
built into it, so the driver must consume many CPU cycles.
In such instances, we suggest that you back up your system while in
single-user mode (which is a good idea in any case).
