jarmo@ae.tut.fi (Jarmo Sorvari) (06/07/91)
A friend told me that 8 mm tapes hold their data RELIABLY for only something like 6 months. The media never was designed for digital storage, and the bits sort of "leak through" the base material. Winding and unwinding periodically would slow down a bit this degradation. Is this true? How is it with DAT tapes? I'm sure this is an important factor for many, when deciding between 8 mm and DAT. -- ----------------------------------------------------------------------------- ! Jarmo Sorvari Control Engineering Laboratory ! ! jarmo@ae.tut.fi Tampere University of Technology ! --------------------------------------- BOX 527, 33101 Tampere, Finland -----
kev@hpcpbla.HP.COM (Kevin Jones) (06/18/91)
> A friend told me that 8 mm tapes hold their data RELIABLY for only > something like 6 months. The media never was designed for digital > storage, and the bits sort of "leak through" the base material. > Winding and unwinding periodically would slow down a bit this > degradation. > > Is this true? How is it with DAT tapes? I'm sure this is an > important factor for many, when deciding between 8 mm and DAT. HP quotes 10 years for DDS DAT (data archive life). This figure is based mostly on Japanese research. (This makes some sort of sense in the audio perspective: nobody would buy a pre recorded DAT tape of their favorite artist if they knew that in 6 months the recording would have decayed beyond readability). DDS DAT has additional 3rd layer of error correction on top of the 2 layers provided by the audio format on which DDS is built. This gives more immunity from tape decay than plain audio DAT. DDS DAT also uses read-after-write during recording and repeats bad frames, thus avoiding data integrity problems caused by media defects. I can't comment much on 8mm. The tape used for 8mm is basically the same stuff (metal particle tape) as is used in DAT. Differences in archive life between the two technologies might therefore depend on which has the most effectve ECC. As is the case with all magnetic media, the archive life is VERY dependant on storage conditions. CONSTANT temperature, low humidity and screening from magnetic fields will help a lot. > bits sort of "leak through" the base material. This is a known problem with all magnetic tapes. A 'wrap' on a tape spool "prints" its magnetic image onto a neighbouring wrap. The standard way to avoid this is a pereodic wind from end to end which causes the tape to be re-packed thus changing alignment of data on adjacent wraps. I would be surprised if this phenomena caused a tape to become unreadable within 6 months. (DDS = Digital Data Storage. A format for recording computer data on Digital Audio Tapes developed by HP and SONY and licenced to many other manufacturers of DAT products for data storage). ----------------------------------------------------------------- Kevin Jones. | Hewlett Packard Ltd, | Computer Peripherals Bristol, kev%hpcpbla@hplb.hpl.hp.com | Filton Road, | Stoke Gifford, Tel: 011 44 272 799910 (ext 22351) | Bristol. BS12 6QZ. | ENGLAND. ----------------------------------------------------------------- This response does not represent the official position of, or statement by, the Hewlett-Packard Company. The above data is provided for informational purposes only. It is supplied without warranty of any kind.