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Sun partially circumvents this situation by deploying most of its MirrorStore replication appliances as data movers and using them for one-time replication requirements. Used that way, MirrorStore leaves the primary I/O path between the server and storage array intact. Instead, MirrorStore is given read-only access to the LUNs assigned to the server on the storage array. With this block-level access, MirrorStore migrates LUNs from the existing storage array to the new one in the background, while tracking changes to LUNs on the old array and moving those blocks as the changes occur.
Once all of the data on the LUNs is on the new array, the application is stopped so that the final writes can be synchronized by MirrorStore to the LUNs on the new storage array. The SAN is then reconfigured to allow the server to access the LUNs on the new array, and the server discovers the data on these new LUNs dynamically or is rebooted to allow LUN discovery to occur. The application is then restarted using data that resides on the LUNs on the new storage array.
This was first published in November 2005