Is HSM ready for open-systems storage?


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The drive to better align data storage policies to business needs is spurring the development of new storage management tools. Two goals are improved efficiency of assets through better utilization and greater effectiveness of people through automation. These goals converge in a renewed effort underway by several vendors to reintroduce a technology that's been around for many years--hierarchical storage management (HSM).

This time-honored mainframe technology (see "

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When disk wasn't cheap") never caught on in the Windows and Unix worlds. But changes in technology suggest you should take another look at HSM. And if you're thinking of implementing HSM, consider how to integrate HSM into your open systems environments.

A solution in search of a problem? Several factors have combined to limit the adoption of HSM in open systems, notably:

  • Dramatically falling prices for disk storage
  • Distributed nature of open systems environments
  • Fundamental characteristics of open system apps
Traditionally, the driving force behind HSM was the high cost of disk storage. With costs now falling to less than a penny per megabyte, it may appear at first glance that HSM's problems have disappeared. Certainly over the years, it's been far easier for system administrators to increase storage capacity than to attempt to squeeze efficiency out of every disk drive.

This practice resulted in an increase in overall capacity, while utilization rates fell. Although this was wasteful, as long as the emphasis was on the cost of acquisition rather than the cost of management, it seemed reasonable. However, as administrative costs have begun to outstrip hardware costs, IT managers have renewed their interest in any option that can mitigate these costs.

The decentralized nature of open systems also discouraged the adoption of HSM. In the days of non-centralized, direct-attached storage (DAS), the opportunity to reallocate excess storage didn't exist. It wasn't worth the effort to recoup space from a particular system because there wasn't a way to effectively reassign it. With the onset of storage networks, reallocating storage has become more practical, so this objection no longer applies in many environments.

Nor does the issue of open systems' more interactive (vs. mainframe's) character. Open-systems applications tend to be highly interactive, whereas mainframes--to a large extent--perform huge quantities of batch processing. And the interactive nature of open-systems apps doesn't work well with HSM. If you directly applied the mainframe approach to open systems, when users attempted to access a document, for example, they'd be faced with an hourglass icon for several minutes. The potential increase in help desk calls alone is enough to discourage adoption of HSM. That problem is particularly apparent when tape is the target media for HSM data.

Application-focused HSM/HSM-related products
Legato EmailXtender Supports Exchange and Lotus Domino. Part of a family of HSM and archiving products.
Legato DiskXtender Database Edition Supports Oracle databases. Part of a family of HSM and archiving products.
CommVault QiNetix DataMigrator Integrates with CommVault Galaxy backup software.
Educom Exchange Archive Solution (EAS) A full-featured archiving application for Exchange that includes HSM-related features.
KVS Enterprise Vault for Exchange A full-featured archiving application for Exchange that includes HSM-related features.

This was first published in May 2003

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