Re: tape backup from remote

From: Christoph Sold (cs_at_cheasy.de)
Date: 03/29/04

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    To: freebsd-isp@freebsd.org, sellis@telus.net
Date: Mon, 29 Mar 2004 22:11:51 +0200

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    On Monday 29 March 2004 20:33, Sean Ellis wrote:
    > Hello,

    G'day,

    > I have a very general question about backing up to tape from a remote
    > computer. The tape drive is unfamiliar territory for me, and I'm
    > looking for recommendations for a sequence of steps to take.

    Wise decision.

    > Both machines are running fbsd 4.*, the local machine is a recent 4.9
    > STABLE, and the tape drive is a Conner CTD800R-S. Will it be
    > possible, or advisable, to use a utility to back up over the net
    > directly to the tape, or should we be creating a local mirror and
    > backing up this?

    Backing up remotely can yield _very_ unsatisfying results for several
    reasons:
    - - If there is not enough bandwith, the tape "trashes": After backing up
    a few blocks, the tape has to stop, rewind, then re-synchronize and
    append to the previously written data. This is _much_ slower than
    nominal backup speed.
    - - If the network latency is too high, the backup software may get
    confused and abort.
    - - If the connection is dropped during backup, may tools invalidate the
    whole backup.

    There are both commercial as well as open source tools dealing with this
    situation. I used amanda (in the ports) to backup multiple remote
    clients to one backup machine. Never experienced any data loss during
    restore.

    > I know that these are very basic questions, but I felt that posting
    > here in isp might give me a more informed response.

    Have a look at http://www.thestoragegroup.com/pubs.html , the links
    there show many aspects of backup and recovery.

    Another hint, though: DDS (DAT) is not up to the job. I personally
    ditched all DDS devices after multiple data loss events being caused by
    worn tapes, never properly written tapes, over-aged tapes. Never
    happend with DLT, though.

    HTH
    - -Christoph Sold
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