Block-Level Tiering is a Storage-Centric Solution
Block-level tiering was first introduced as a technique within a storage array to make the storage box more efficient by leveraging a mix of technologies such as more expensive SAS disks as well as cheaper SATA disks. As the name implies, block-level tiering moves blocks between the various tiers to increase performance while reducing costs. Hot blocks and metadata are typically kept in the higher, faster, and more expensive storage tiers while cold blocks are migrated to lower, less expensive tiers
File-Level Tiering is a Data Management Solution
File-tiering is a more advanced technology and is standards-based. File-level tiering means the file along with all its metadata moves to the new tier. Whether you have NTFS extended attributes or Posix ACLS you need the ability to move the file and all of its associated metadata with high fidelity and rehydrate it back into its exact original form if needed. Moving just the file is not enough. Many applications rely on attributes of the file to operate. The file system imposes access control through basic and extended attributes. File-level tiering maintains full file fidelity and preserves all the attributes and metadata along with the file at each tier.