Wednesday, October 10, 2012

logshipping vs mirroring

    Database Mirroring benefits:
        Instantaneous synchronization of changes
        Easy setup and maintenance
        Automated failover (in High Availability Mode)
        Easy to perform failover
        Fast failover. (if no transactions are queued)
        Applications can be mirroring aware using failover partner parameter in connection string

    Database Mirroring limitations:
        Limited number of databases can be mirrored per SQL instance. (however, this number is higher than the 10 you see plastered everywhere, but really depends on your hardware)
        Mirrored database cannot be queried, backed up, or basically touched in any way (snapshot can be taken however)
        Only supports one to one server pairings
        Cannot mirror a database more than once
        Synchronous mirroring is intolerant to latency and bandwidth constraints (Asynchronous mirroring has no problems with latency or bandwidth)

    Log Shipping benefits:
        Very flexible - Independent jobs govern backup/copy/restore behavior
        Delay of restore job can protect from database corruption
        Log shipped database can be queried. (in standby mode)
        Log shipping allows multiple standby databases
        Perhaps more tolerant to latency than sychronous mirroring.
        Doesn't affect performance of primary server
        Easy setup

    Log Shipping limitations:
        No automated failover
        Cannot synchronize faster than once a minute
        Failover is more complicated than mirroring
        Harder to view status of log shipping

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