In a VxFS file system with an active file placement policy, the placement class on whose volume a file resides is part of its metadata, and is attached when it is created and updated when it is relocated. When an application extends a file, VxFS allocates the incremental space on the volume occupied by the file if possible. If not possible, VxFS allocates the space on another volume in the same placement class. For example, if a file is created on a
tier1 volume and later relocated to a
tier2 volume, extensions to the file that occur before the relocation have space allocated on a
tier1 volume, while those occurring after to the relocation have their space allocated on
tier2 volumes. When a file is relocated, all of its allocated space, including the space acquired by extension, is relocated to
tier2 volumes in this case.