Question about capacity

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

  1. Dirk Wagner

    Dirk Wagner Guest

    Hi,

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

    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?

    Thanks

    Dirk
     
    Dirk Wagner, Feb 10, 2014
    #1
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  2. Dirk Wagner

    Michael Arm Guest

    Most likely the amount of compression/
    Mike
     
    Michael Arm, Mar 9, 2014
    #2
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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...

    Ciao

    dirk
     
    Dirk Wagner, Mar 10, 2014
    #3
  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
    #4
  5. Dirk Wagner

    Dirk Wagner Guest

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

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

    Thanks

    Dirk
     
    Dirk Wagner, Mar 10, 2014
    #5
  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
    #6
  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
    tapes...

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

    Thansk

    Dirk
     
    Dirk Wagner, Mar 11, 2014
    #7
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