DAT Tape Drive to Backup.

DAT Tape Drive to Backup.

1 - When you give a command backup, the program checks the file allocation table of the hard disk to
find those that will be copied. Then the program copies the data file to file to the buffer unit
digital audio tape (DAT), which generally behaves 512KB to 1MB of data. As in the case of QIC tape drive, the
DAT drive applies an algorithm to the data to create a code error correction that is added to the data contained
in the buffer.

2 - It is the unique design of the head read / write units DAT which lets you copy large amounts of
data in a tiny cartridge of similar size to a matchbox. The mechanism is a rotating cylinder with
four heads separated by 90 degrees. Two of them, the recording heads A and B, write the data to be
copying, and the other two reading verify the data. The cylinder tilts slightly so you can rotate according
the angle of the tape. It rotates 2,000 times per minute while the tape passes in front of the cylinder in the opposite direction
rotating at a speed of 1/3 inch per second.

3 - While The recording head maintains contact with the tape are recorded approximately 128KB of data and correcting codes
Error buffer unit for a track of the tape. As the cylinder is inclined to one end of the head is
tape at the beginning of the read head and moves diagonally across the tape to find the other end. This raises
a narrow diagonal eight times longer than the width of the tape.

4 - The read head reads the data back and checks the track, bit by bit, comparing them with the data still
are in the buffer. If the tape data are correct, are removed from the buffer and more data is read from the hard drive.
If the data contained in the present track errors will be recorded again in the next passage.

5 - The recording head B passes through the tape and writes data on a track with 40 degree angle relative to the track,
performing a type of intersection that overlaps the track A. The overlapping data store for more information
inch tape, and are not confused later because the magnetic bits written by the two heads have
different polarity, and the other two heads only read data tracks correctly aligned.

6 - reading head B recording and B satisfy the same process steps alternating with the other heads A until
all data has been copied. Then, the unit rewinds the tape and writes the directory of the files stored
a special part in the beginning of the tape or a hard disk file.

Note - To restore files from a DAT drive, the program reads the directory, move the tape to the starting position
where are the files you want and copy them to the hard drive.

Source: Evolution of Computers