PowerStore uses redirect-on-write technology for all writes entering the system. When a resource writes to a location which is shared with another resource or by a snapshot, the data is redirected to a new location and the resource pointers are updated to reference the new location. The following figure provides an example of redirect-on-write technology.
In this example, a storage resource contains four blocks of data: A, B, C, and D. A snapshot is taken of the storage resource to preserve this point-in-time, and points to blocks A, B, C, and D. When the host/client modifies blocks B, A, then D, the data is written to new locations on the system. The pointers for the storage resource are then updated to reflect the new locations for B’, A’, and D’. This example assumes that no data-reduction savings are achieved. For more information about data reduction within PowerStore, see the white paper on the .