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Essentially, this document is GPL'ed.

Early tapes were ferrite based. In the 1980's, the media formulation was changed to chromium dioxide. This was superceeded in the 1990's by metal particle media.

All data stored on tape is at risk. The rule of thumb is that after 10 years, the media is suspect and may not be read reliably. Do not store critical information on tape without a regular program of copying and reverification.

A related problem is that tape devices are being improved, and older devices are retired. At some point, no devices will be available to read the media. Even if the tape transport itself exists and works, the interface to the host computer may no longer exist. IBM supports 4 mainframe peripheral connectivity options, Parallel, ESCON, FICON, and SCSI.

Finally, unless data is stored in a simple flat format, it is likely that the backup, restore, reload software will not be available and it will not be possible to decypher the data.

If your tape library is not IBM 3590, IBM 3590E, STK 9840, STK Redwood, or similar, your data is at risk.

Media Description	Density	Capacity	Com press ion	JCL	Device Name	Era
7 track round	800 bpi	20 meg		den=2	2400	1960's
9 track round	1600 bpi	45 meg		den=3	2420	late 1960's-1970
9 track round	6250 bpi	150 meg		den=4	3420	1970's
18 track	Standard (readable on 3480, 3490 and 3490E)	200 meg	3:1		3480	1980's
18 track		200 meg	3:1		3490	Early 1990's
36 track	Standard	400 meg	3:1		3490E	Early 1990's
36 track	Enhanced	800 meg	3:1		3490E	Early 1990's
36 track	Quad length	1600 meg			Timberline (3490E clone)
128 track	Standard Magstar	10 gig	4:1		3590	Mid 1990's
128 track	Enhanced Magstar (readable on 3590 and 3590E only)	20 gig	4:1		3590	Mid 1990's
		20 gig			STK 9840	Mid 1990's
256 track	Standard	20 gig	4:1		3590E	Late 1990's
256 track	Enhanced	40 gig	4:1		3590E	Late 1990's
RDW	length 1	10 gig			STK Redwood	Late 1990's
RDW	length 2	25 gig			STK Redwood	Late 1990's
RDW	length 3	50 gig			STK Redwood	Late 1990's

This page is abstracted from Internet postings and vendor web pages. Please submit corrections and updates to HHResCo@ATTGlobal.net. Submission should be sent as ASCII text not as Microsoft Word attachments.

Information in the table was derived from USENET articles by

bblack@FDRINNOVATION.COM (Bruce Black)

mycroft@DALLAS.NET (Russell Witt)

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