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Data protection is especially critical, so IT managers might feel more comfortable with a "belts and suspenders" approach. Even if the archiving software places some data off-limits by policy, a basic storage system used as the archive target may leave it unprotected. Although careful application of traditional security and access controls found on standard NAS systems can offset this risk, the enhanced features of specialized archiving storage systems go further.

Storage platforms specifically designed for archiving often include enhanced protection against modification or deletion, sometimes called write once, read many (WORM) storage. Contrary to popular belief, there are few regulations or laws specifically calling for WORM storage. But the concept of access control is as central to long-term data management as retention schedules and classification, and legal discovery regularly demands certification that data hasn't been accessed or modified. Therefore, no legal or compliance archive should be without WORM capability. Systems may also offer authentication that uses mathematical checksums to verify that data hasn't been modified, but use of those haven't yet been commonly presented in legal cases. Finally, make sure the system logs and reports all access attempts, as this data is critical for documenting compliance.

Many storage systems designed for archiving are now adding data-reduction technologies ranging from compression to single-instance storage

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(SIS) to advanced deduplication. These various technologies function similarly, using algorithms to reduce the amount of data that must be stored in a lossless fashion. Single-instance storage compares whole files or objects with existing content, storing only a single copy of duplicates. Traditional data compression encodes files or objects, creating a "dictionary" of repeating patterns to shrink them. Finally, deduplication technology searches for duplicate data both within objects and across the entire data store, a complex computing task that can result in vastly reduced storage requirements. Each approach balances storage reduction against the computing power required to accomplish it.

These specialized archiving systems also include standard enterprise storage capabilities like scalability, high availability and data replication. Architecture varies from product to product, with some employing traditional storage array technology and others based on a cluster of redundant nodes. One differentiator is the extent to which the archive system can, or should, include non-archive data (see "Consolidated vs. unified storage," below).

Consolidated vs. unified storage
As archives are implemented, it's tempting to create "stovepipes" of storage on the back end, with each application using its own storage system for content and indexes. "Of course a unified storage platform gives efficiency of resources and management, but consolidating archives has other benefits," says Rob Mossi, senior marketing manager for archiving at Hitachi Data Systems. "Creating a consolidated platform for the storage of archived content is a winning strategy, especially when leveraging advanced storage system features like duplicate elimination, compression and replication as found in a highly scalable, performance-enabled active archive solutions," he notes.

Although archive software can use a variety of storage platforms to store the archived content itself, there are other storage requirements for these applications. All archiving software products maintain an index of both the production and archived data, and that database is often stored on a conventional storage array. A unified, multiprotocol storage system with conventional block storage and archiving features allows both the index and content to share space, easing management and growth headaches.

This was first published in January 2009

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