You may find tapetype-definitions in the example amanda.conf, in the mailinglist-archives of the amanda-users-mailinglist at http://marc.theaimsgroup.com/?l=amanda-users or in the Amanda-FAQ-O-Matic at http://www.amanda.org/fom-serve/cache/1.html. They inform Amanda how much it is supposed to be able to store in a tape (length), how much space is wasted at the end of a dump image with the EOF mark (filemark) and how fast the tape unit is (speed).

The most inportant parameter is length, since Amanda may decide to delay a backup if length is too small, but, if it is too large, Amanda may end up leaving dumps in the holding disk or having to abort some dump.

Filemark is important if you have many disks, particularly with small incremental backups. The space wasted by so many filemarks may add up and considerably modify the available tape space.

The speed is currently unused.

If none of the sample tapetype entries match your needs, you may search the mailing list archives or look up the on-line list of tapetype entries. Just follow the links from http://www.amanda.org.

Amanda provides the amtapetype utility to calculate the size of a tape, to generate a "tapetype" entry for your amanda.conf.

Specifying the appropriate tape device, but beware that it may take many hours to run (it fills the tape twice ...). Make sure you do not use hardware compression, even if you plan to use hardware compression in the future. amtapetype writes random data to tape, and random data will expand instead of compressing, therefore you'll get an estimate that's smaller than expected.