DLT IV not reaching full capacity - Storage

This is a discussion on DLT IV not reaching full capacity - Storage ; I have a DLT 7000 with brand new Sony DLT IV tapes and when I backup about 60G from several directories using tar on FreeBSD 5.2.1-RELEASE-p13 I can only ever get 45G out of the tape before it falls over ...

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Thread: DLT IV not reaching full capacity

  1. DLT IV not reaching full capacity

    I have a DLT 7000 with brand new Sony DLT IV tapes and when I backup
    about 60G from several directories using tar on FreeBSD
    5.2.1-RELEASE-p13 I can only ever get 45G out of the tape before it
    falls over with:

    Total bytes written: 48194365440 (45GB, 3.6MB/s)
    /usr/bin/tar: /dev/sa0: Wrote only 0 of 10240 bytes
    /usr/bin/tar: Error is not recoverable: exiting now

    Prior to the tar command I collate a file full of sockets and FIFO
    files which I pass to tar in a exclude-from argument, so I would not
    imagine it to be a file to cause the premature end.

    I have tried several SCSI cables and several SCSI cards, I have tried
    many tapes and still I seem to hit this limit. Does anyone have any
    ideas?

    Kind Regards,
    Dean


  2. Re: DLT IV not reaching full capacity

    "Dean Pearson" wrote in message
    news:1110321796.779597.208780@o13g2000cwo.googlegr oups.com...
    >I have a DLT 7000 with brand new Sony DLT IV tapes and when I backup
    > about 60G from several directories using tar on FreeBSD
    > 5.2.1-RELEASE-p13 I can only ever get 45G out of the tape before it
    > falls over with:
    >
    > Total bytes written: 48194365440 (45GB, 3.6MB/s)
    > /usr/bin/tar: /dev/sa0: Wrote only 0 of 10240 bytes
    > /usr/bin/tar: Error is not recoverable: exiting now
    >
    > Prior to the tar command I collate a file full of sockets and FIFO
    > files which I pass to tar in a exclude-from argument, so I would not
    > imagine it to be a file to cause the premature end.
    >
    > I have tried several SCSI cables and several SCSI cards, I have tried
    > many tapes and still I seem to hit this limit. Does anyone have any
    > ideas?
    >
    > Kind Regards,
    > Dean


    You get what you paid for. A DLT-7000 is 35GB native, minus some tar and
    tape handling overhead you can expect about 32GB or so available. With 45GB
    on tape you are getting 1.4:1 compression out of the drive. Nothing wrong
    with your system.

    Rob



  3. Re: DLT IV not reaching full capacity

    1.4:1 is about typical for a full system backup. The 2:1 marketing
    figure applies to text files (sometimes.) With some files you can get
    higher compression factors (rarely), with uncompressible files (e.g.
    JPEG, MPEG or .gz) you'll even get less than 1:1 - in which case it
    makes sense to turn compression off.

    Ralf-Peter


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