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Analysis: Information Lifecycle Management: Page 9 of 29

Unstructured data is much messier. For e-mail, we have sender, recipient, date and content. For other files we have several possible sources from which to derive value. The most obvious is file system metadata in your servers or NAS devices. Modern file systems, from Linux's ext3 to Network Appliance's WAFL, store file-creation, last-modified and last-accessed dates along with file attributes like "hidden," "read only" or "this file is stored offline."

Each file also has security information attached, including an access control list and, for most systems, a file owner. Conventional HSM (hierarchical storage management) solutions use the "file last accessed" date as their only indication of value, migrating files after they have not been accessed for a given period.

As we discuss in "A Fine Metamess," page 48, there are problems with using file system metadata to classify files. Even so, some data-management systems, including Arkivio's Auto-stor and Kazeon Systems' appliances, rely on file system metadata as their only information source.

Fortunately, most files have additional embedded metadata that give file-classification applications more to work with; for example, a JPEG could have an embedded date years before the file-system creation date. Unfortunately, most users don't go to the effort of entering even basic metadata, like subject, into their files.

Classification products, including Abrevity's FileData Classifier and Manager, Scentric's Destiny and EMC's Infoscape, create an index of file content and allow IT to create policies based on key words or phrases. Better than depending on users, but still a pretty crude indication of a file's value or sensitivity.