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Several questions regarding database mirroring. RRS feed

  • Question

  • Our company is looking to move to a more robust database platform/setup, and it looks like sql 2005 + database mirroring is what we are looking for. First I have some questions about it.

    Can a server that is functioning as a mirror for one database be the primary server for a seperate database? Basically think of a triangle of three sql servers, each serving as a primary server for a specific database, and using the next server in the triangle as a mirror for that specific database. To be more specific:

    Server 1, Primary Database A, Mirroring Database C
    Server 2, Primary Database B, Mirroring Database A
    Server 3, Primary Database C, Mirroring Database B

    If that is possible, how many witness servers would be needed to accomplish the above topology? On that note, how robust hardware wise should the witness server be?

    On a completely seperate note, what method is recommended for interconnecting these servers? Is gigabit ethernet fast enough, or does it require something like fibre channel or infiniband?

    Thank You!
    Tuesday, January 31, 2006 3:08 PM

Answers

  • The above configuration is supported for mirroring. In fact they could also be used as a witness as well.

    So, Server 3 could be a witness for database A, and Server 2 could be a witness for database C, etc.

    Now as a best practice, I would recommend a dedicated mirror to simplfy the design. In general, a less complicated design will be more reliable that a more complicated design.

    The witness doesn't need very performant hardware, but it must be robust. It is one of the servers that allows for automatic failover. But a dedicated laptop running express would be a reasonable witness; it is designed for withstanding some physical punishment and it has a dedicated battery power supply.

    As to how big a network you need depends completely on how much log you generate for you load. In general, mirroring works best with faster networks.

    Thanks,

    Mark

    Wednesday, February 1, 2006 11:25 PM