When a file that has been moved is accessed, HSM will automatically demigrate a file from the slower device back to the faster device. On-line storage devices are those that provide immediate access to data. Hard disks and RAM are the most common types of on-line storage. Near-line storage devices are those that provide slower access to data. Off-line storage devices are the least expensive and slowest of the storage devices.
Tapes are the most common off-line devices.
Whereas MO disks can access data in a matter of seconds, accessing data on tape can take many minutes. HSM complements, but is not a replacement for data backup. A data backup will help restore data after an accident or catastrophic failure of the storage device. The purpose of HSM is to manage data storage and administration. HSM Toolkit 1.0 is FWB's version of HSM for the Mac.