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  1. #1
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    Unanswered: Has any one ever used Double Take?

    http://oldbbs.dlbaobei.com/qwer1234/...dWx0LmFzcHg%3D

    My concern is this ..


    Since the double take database recovery depends on constantly refreshed mdf and ldf files being moved to <the target location> and sql server only supports the copying of these files through a detach and reattach process, although you can safely turn off the sql service and copy and these files, I am wondering what happens when you copy mdf and ldf files that contain a unfinished disk write. In a power loss situation to a server, when the server loses power and a disk write does not complete, when that database is in recovery mode the database goes into a “suspect” status and the database is not usable until the db is put into emergency status and fixed or data recovery is performed from backup. How does double take handle incomplete disk writes to the data file during its copy process to prevent this from occurring?


    Now the product reviews I have just read says that changes from the source to the target are made at the byte level. So if a byte is changed, that byte is moved to your target server. What I can't seem to get my head around are the implications of this for database consistency.

    Anyone have any light to shed for me?
    “If one brings so much courage to this world the world has to kill them or break them, so of course it kills them. The world breaks every one and afterward many are strong at the broken places. But those that will not break it kills. It kills the very good and the very gentle and the very brave impartially. If you are none of these you can be sure it will kill you too but there will be no special hurry.” Earnest Hemingway, A Farewell To Arms.

  2. #2
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    Sorry dude...what do you need to use a product like that for?
    Brett
    8-)

    It's a Great Day for America everybody!

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    I'm Good Once as I ever was

    The physical order of data in a database has no meaning.

  3. #3
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    Jan 2003
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    We use it here. So far, it has worked out very well. The only problem we had was when the mirroring process had not finished, and someone tried to fire up the target database. If you have a power outage at your main site, you may lose a few transactions at the destination side, but it is a lot better than trying to get tapes assembled, in the drive, etc., etc..

    We even test the system 3 or 4 times a year. In 3 years or so of doing it this way, I have yet to have a complaint from the OS admins who run my scripts to get the databases back online down there (What? You think they send me to do the recovery tests?).

  4. #4
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    Not my idea and I am mad busy (no time to impliment sql replication) and we are doing that whole ASP thing and need to replicate data offsite to another data center, since this sql server in the other data center will not be running sql server until we need it, we save on licencing etc.... lalalalalalala. My environment is totally crazy.
    “If one brings so much courage to this world the world has to kill them or break them, so of course it kills them. The world breaks every one and afterward many are strong at the broken places. But those that will not break it kills. It kills the very good and the very gentle and the very brave impartially. If you are none of these you can be sure it will kill you too but there will be no special hurry.” Earnest Hemingway, A Farewell To Arms.

  5. #5
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    how much does it cost?
    Brett
    8-)

    It's a Great Day for America everybody!

    dbforums Yak CorralRadio 'Rita
    dbForums Member List
    I'm Good Once as I ever was

    The physical order of data in a database has no meaning.

  6. #6
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    dunno. cheaper than a sql proc license. they just invite me to stuff to give sales people a hard time.
    “If one brings so much courage to this world the world has to kill them or break them, so of course it kills them. The world breaks every one and afterward many are strong at the broken places. But those that will not break it kills. It kills the very good and the very gentle and the very brave impartially. If you are none of these you can be sure it will kill you too but there will be no special hurry.” Earnest Hemingway, A Farewell To Arms.

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