Question about capacity

Discussion in 'Backup Software' started by Dirk Wagner, Feb 10, 2014.

  1. Dirk Wagner

    Dirk Wagner Guest


    I am using a HP Ultrium 215 with LTO1 tapes for backing up our

    Yosemite Server Backup shows a "native total capacity" of 97,87GB for
    each of tapes.

    But the size of written data differs from tape to tape.
    If this would be arround 5 to 10 %, I would not take care - but there
    are tapes which have stored 65GB on it, and others, which hold 145GB.

    ALL tapes are HP 100/200GB LTO1 and all are running the same
    backup-cript, so there should be the same data on each of the tapes.

    Any ideas, why there is such a difference in capacity?


    Dirk Wagner, Feb 10, 2014
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  2. Dirk Wagner

    Michael Arm Guest

    Most likely the amount of compression/
    Michael Arm, Mar 9, 2014
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  3. Dirk Wagner

    Dirk Wagner Guest

    There is a complete backup of ALL the data running.
    So there might be some new files on a new backup - but this would be a
    maximum of 10 GB.
    And this would be mostly Word and Excel-Files, so the rate of
    compression should not differ that much...


    Dirk Wagner, Mar 10, 2014
  4. Dirk Wagner

    Bob Willard Guest

    As tapes age, they develop bad spots, which reduces capacity. And,
    aging is aggravated by improper care: mag.tape is sensitive to storage
    conditions (temperature and humidity and electromagnetic fields) and to
    handling conditions).

    On the old Colorado Trakker tapes I once used for SOHO backup, some old
    tapes were reduced by a lot (maybe 20%? I don't recall) due to bad
    spots. And, backup/restore time increased exponentially due to
    shoeshining over bad spots.
    Bob Willard, Mar 10, 2014
  5. Dirk Wagner

    Dirk Wagner Guest

    so as a tape gets older, it gets more bad spots and the capacity

    I must check, if this fits with the age-table of my tapes...


    Dirk Wagner, Mar 10, 2014
  6. Dirk Wagner

    Bob Willard Guest

    I stated that badly; sorry. Yes, time take its toll, but the major
    cause of deterioration is usage.

    I had one piece of tape that I intentionally abused with an old IBM 729
    reel-to-reel tape drive. After enough (ab)use, one section became
    nearly transparent: most of the mag.particles had been knocked off
    by the tape drive.
    Bob Willard, Mar 11, 2014
  7. Dirk Wagner

    Dirk Wagner Guest

    OK - this tapes were in a 2-weekly rotation for about 4 years now.
    Only tapes, that were used on the last day of a month were taken out of
    the rotation...

    Within 4 years thes would be about 200 writing-circles for some of the

    OK - I will replace them earlier in the future ;-)


    Dirk Wagner, Mar 11, 2014
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