Today, hierarchical storage management (HSM) is usually found in installations
that have large volumes of data that are used seldom, sporadically,
or periodically. Current work in includes extending it to provide full
information life-cycle management (ILM) Here, data move from disk to tape
and back to disk, as needed, but are deleted on a schedule or according to
policy. For example, some sites save e-mail for seven years but want to be sure
that at the end oi seven years it is destroyed. At that point, the data could be
on disk, HSM tape, and backup tape. ILM centralizes knowledge of where the
data are so that policies can be applied across all these locations.