Three ways of solving data migration problems

Server volume managers and virtualization aren't the only solutions

Clustered storage represents one of the more significant trends in storage right now and for good reason. Clustered storage gives users a path to follow to avoid one of the more unpleasant realities that storage networks create: storage islands.

In most networked storage configurations, storage islands result when companies purchase multiple storage arrays. Though these storage arrays may communicate and even replicate data between one another, the real problem surfaces when one needs to retire a storage array. At that point, users must almost always schedule an application outage for servers attached to that array since the storage array provides no native, nondisruptive way to migrate data to a new storage array.

To date users have circumvented this in a couple of ways. One was to use volume managers on servers that have the capability to discover logical unit numbers or disks on a new storage array and then mirror the data in real time from the old to the new array. The other was to use a network-based virtualization software that resided between the server and storage array and could perform similar nondisruptive data migration functions.

Clustered storage arrays now give companies a third option in which to perform this task nondisruptively. With clustered storage, all storage arrays in a cluster communicate with one another which allows users to copy or move data between them in real time without requiring server or application outages.

Clustered storage arrays such as those from Isilon Systems Inc. still require companies to standardize on their products to deliver this functionality and do not address concerns about how to manage storage arrays companies may already own. But for companies that want to simplify storage management and standardize on a specific vendor's product, clustered storage arrays provide a viable alternative that avoid a key shortcoming of storage networks.

Jerome Wendt is the president and lead analyst with DCIG Inc. He may be reached at

Copyright © 2007 IDG Communications, Inc.

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