You run aggregate reallocation scans to optimize the location of physical blocks in the aggregate. Doing so increases contiguous free space in the aggregate.
You run an aggregate reallocation scan using the reallocate start -A command.
Aggregate reallocation does not optimize the existing layout of individual files or LUNs. Instead, it optimizes the free space where future blocks can be written in the aggregate. Therefore, if the existing layout for a file, LUN, or volume is sub-optimal, run a file, LUN, or volume reallocation scan.