Alternatives to mirroring

Mirroring, as explained in this manual, is a database server feature. Your operating system or hardware might provide alternative mirroring solutions.

If you are considering a mirroring feature provided by your operating system instead of database server mirroring, compare the implementation of both features before you decide which to use. The slowest step in the mirroring process is the actual writing of data to disk. The database server strategy of performing writes to mirror chunks in parallel helps to reduce the time required for this step. (See Disk writes to mirror chunks.) In addition, database server mirroring uses split reads to improve read performance. (See Disk reads from mirror chunks.) Operating-system mirroring features that do not use parallel mirror writes and split reads might provide inferior performance.

Nothing prevents you from running database server mirroring and operating-system mirroring at the same time. They run independently of each other. In some cases, you might decide to use both the database server mirroring and the mirroring feature provided by your operating system. For example, you might have both database server data and other data on a single disk drive. You can use the operating-system mirroring to mirror the other data and database server mirroring to mirror the database server data.


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