Re:Re: Second Data Center for Disaster Recovery

  • 1.  Re:Re: Second Data Center for Disaster Recovery

    Posted 11-05-2009 06:55 PM
    Hmmmm. I would wonder about what happens if the replication of data
    volumes (relatively low update level) is allowed to proceed ahead of the
    replication of journal volumes (relatively high level of updates).

    Without knowing the technical details of the solution you're using, I'm
    assuming it shoves things down the pipe as fast as it can, and applies
    it on the far end as fast as it can. All this without attempting to
    keep things in exact timestamp order across different datasets or
    volumes. I would assume it makes this tradeoff in order to avoid
    impacting write throughput on the ""live"" side.

    IF this can happen, then you might have warmstart/integrity issues.
    Chances are probably low, but not zero. The short answer is if the jrnl
    replication runs behind the database replication, you WILL have images
    on the database files for which you lack sufficient jrnl data to remove
    (incomplete or aborted run-units).

    Don Casey
    Principal Consultant
    Run Right, LLC