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 not optimal, run a file, LUN, or volume reallocation scan. For example, after adding new disks to an aggregate, if you want to ensure that blocks are laid out sequentially throughout the aggregate, you should use reallocate start -f on each volume instead of reallocate start -A on the aggregate.