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optical disk front ends that act as a high speed cache. The HSM
management software attempts to “anticipate” the file usage needs
of your users, based on criteria you set.
Files may be moved to progressively deeper storage based on the
date they were last used or the importance of the files. Newer or
more critical files may be kept on the HSM’s hard disk cache for
fast recall. As these files age, they may be moved off to storage in
the system’s tape library.
The challenge that HSM poses to IS managers is that HSM’s deep
storage tapes are generally not sent off site or archived in a tradi-
tional manner. HSM is active near-online storage and not a data
backup system. When data is moved further out in the hierarchy
by the HSM, a marker or pointer is left on the network server. This
pointer tells the HSM software where the file is located for
retrieval.
Your backup software must know what these pointers mean and, if
necessary, request the file from the HSM for inclusion in your full
backups. Not all backup management systems have this capability.
You should check with your HSM vendor to make sure the HSM
can be integrated with your backup management system.
With HSM systems, it’s important to consider the quality of the
deep storage component. Unlike normal backup systems, HSM tape
drive utilization will be on the order of 80 percent or more. The
drives and media used must be reliable and proven to withstand the
heavy use it will be subjected to. DLTtape drives have become the
standard for many HSM system vendors due to their inherent relia-
bility, high density data storage, and high speed transfer rates.
HORIZONTAL APPLICATIONS
9.6