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Performing a full reallocation scan of a LUN, file, or volume

You can perform a scan that reallocates every block in a LUN, file, or volume regardless of the current layout by using the -f option of the reallocate start command. A full reallocation optimizes layout more aggressively than a normal reallocation scan. A normal reallocation scan moves blocks only if the move improves the layout of a LUN, file, or volume. A full reallocation scan always moves blocks, unless the move makes the layout even worse.


Using the -f option of the reallocate start command implies the -o and -n options. This means that the full reallocation scan is performed only once, without checking the layout first.

You might want to perform this type of scan if you add a new RAID group to a volume and you want to ensure that blocks are laid out sequentially throughout the volume or LUN.

Attention: You can not perform a full reallocation (using the -f option) on an entire volume that has existing Snapshot copies, unless you also perform a physical reallocation (using the -p option). Otherwise, an error message displays. A full reallocation on a file or LUN without the -p option might result in using significantly more space in the volume, because the old, unoptimized blocks are still present in the Snapshot copy after the scan. For individual LUNs or files, avoid transferring large amounts of data from the Snapshot copy to the active file system unless absolutely necessary. The greater the differences between the LUN or file and the Snapshot copy, the more likely the full reallocation will be successful.


  1. Enter the following command: reallocate start -f [-p] pathname | vol/volname

    -p reallocates user data on the physical blocks in the aggregate while preserving the logical block locations within a flexible volume. You can use this option only with flexible volumes or with files and LUNs within flexible volumes.