Mirroring is a strategy that pairs a primary chunk of one defined dbspace, blobspace, or sbspace with an equal-sized mirror chunk.

Every write to the primary chunk is automatically accompanied by an identical write to the mirror chunk. This concept is illustrated in the following figure. If a failure occurs on the primary chunk, mirroring enables you to read from and write to the mirror chunk until you can recover the primary chunk, all without interrupting user access to data.
Figure 1. Writing data to both the primary chunk and the mirror chunk
This figure shows arrows pointing from the database server to both the primary chunk and a mirror chunk.

Mirroring is not supported on disks that are managed over a network. The same database server instance must manage all the chunks of a mirrored set.

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