To manage reallocation scans, you must enable reallocation scans on your storage system. Then you define a reallocation scan to run at specified intervals or on a specified schedule.
You can define only one reallocation scan per file, LUN, volume, or aggregate. You can, however, define reallocation scans for both the aggregate (to optimize free space layout) and the volumes in the same aggregate (to optimize data layout).
You can also initiate scans at any time, force Data ONTAP to reallocate blocks sequentially regardless of the optimization level of the LUN layout, and monitor and control the progress of scans.
A file or LUN reallocation scan is not automatically deleted when you delete its corresponding file or LUN. This allows you to reconstruct the file or LUN without having to re-create its reallocation scan. If the file or LUN has not been re-created in time for the next scheduled run of the reallocation scan, the storage system console displays an error message. A volume or aggregate reallocation scan is automatically deleted when you delete its corresponding volume or aggregate.
You can perform reallocation scans on LUNs or aggregates when they are online. You do not have to take them offline. You also do not have to perform any host-side procedures when you perform reallocation scans.