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Reasons to use LUN, file, or volume reallocation scans

You run LUN, file, or volume reallocation scans to ensure that blocks in a LUN, file, or volume are laid out sequentially.

If a LUN, file, or volume is not laid out in sequential blocks, sequential read commands take longer to complete because each command might require an additional disk seek operation. Sequential block layout may improve the sequential read performance, and usually the write performance, of host applications that access data on the storage system.

You run a LUN, file, or volume reallocation using the reallocate start command. If you add disks to an aggregate, you can redistribute the data equally across all of the disks in the aggregate using the reallocate start -f command.

Note: A volume reallocation scan computes the average level of layout optimization over all the files in the volume. Therefore, a volume reallocation works best if a volume has many files or LUNs with similar layout characteristics.