BACKUP AND RECOVERY,How A Tape Drive Interfaces With A Computer,Tape Writing Method,Tape Formats And Tape Type

How A Tape Drive Interfaces With A Computer

A tape drive can be an external or internal device. External tape drives cost more but can be used by several computers. A tape drive interfaces with a computer in these ways:

An external tape drive can use the parallel port, with an optional pass-through to the printer (allowing the drive and printer to use the same parallel port).

An external or internal drive can use the SCSI bus. This method works well if the tape drive and the hard drive are on the same SCSI bus, which contains the data pass-through just to the SCSI system.

An external or internal drive can use its own proprietary controller card.
An external or internal drive can use the floppy drive controller.
An internal drive can use the IDE ATAPI interface.

Currently, the most popular tape drive interfaces are SCSI and IDE ATAPI. The following figure shows the rear of an ATAPI tape drive. You can see the connections for a power supply and 40-pin IDE cable and jumpers to set the drive to master, slave, or cable select. This setup is similar to any IDE device.

When installing an ATAPI tape drive, avoid putting the drive on the same IDE data cable as the hard drive to prevent hindering the hard drive’s performance. A typical configuration is to put the hard drive as the sole device on the primary IDE channel and put a CD-ROM drive and tape drive sharing the second channel. Set the CD-ROM drive to master and the tape drive to slave on that channel.

The Tapes Used By A Tape Drive

Tape drives accommodate one of two kinds of tape:

Full-sized data cartridges are 4 x 6 x 5/8 inches in size.

Smaller mini cartridges, as shown in the following figure, are 3¼ x 2½ x 3/5 inches. Mini cartridges are the more popular of the two because their drives can fit into a standard 5½- inch drive bay of a PC case.

Tape Writing Method

Tape drives write to tape very similar to the way floppy drives write to floppy disk:

There is an FAT at the beginning of the tape that tracks the location of data and bad sectors on the tape. The tape must be formatted before data can be written to it. Many tapes come preformatted from the factory. Make sure to carefully match tapes to tape drives. Some standards exist and have been promoted by different organizations and manufacturers. The following two tables show the tape formats and types that are supported by tape drives, each from a different tape drive manufacturer. The first table shows the Seagate 8 or 20 GB drives that can support QIC-3080 and TR-5 tapes:

The second table shows that the Eagle TR-3 tape mini cartridge tape drive can use either the QIC-3010 or QIC-3020 format and five tape types. Some of these drives are also able to read other formats that are compatible with these formats.

Tape Formats And Tape Type

One of the first efforts to standardize the way data is written to tape was established around 1983 by a group of manufacturers who formed Quarter-Inch Cartridge Drive Standards, Inc. These standards are sometimes called the Quarter-Inch Committee (QIC), or quarter- inch cartridge (standards). Many QIC standards have been developed, but only a few are used today. 3M developed the Travan standard. Travan is backed by many of the industry leaders in tape drive manufacturing. Different levels of Travan standards include TR-1 through TR-5, and each level is based on a different QIC standard.

Tape drives often support a variety of tape types. Even though a tape drive may use a mini-cartridge rather than a data cartridge, not all mini-cartridge tapes can be used in a tape drive. Consult the tape drive’s user guide to find out which tape type you can use with the drive. Mini-cartridge tape drives use more than one type of tape drive mechanism, and more than one density is used to write data to the tape. Since some tape drives don’t format tapes, make sure to buy preformatted tapes.