Somewhere near the top of the list of activities that storage people like doing least is data migration. Slow, time-consuming, and often scheduled at convenient times such as 3 a.m. Sunday morning, it has to rank up there with tasks like disaster recovery testing and SAN reconfiguration. To make matters worse, the process often seems to be a prime candidate for Murphy's Law, often exceeding scheduled windows or needing to be rolled back and rescheduled due to unforeseen problems.

The methods used to perform migrations can vary considerably depending on what, where and how much data is being migrated, and in recent years, the number of technology options has increased significantly. In addition to traditional approaches (for example, host-based migration tools and like-to-like storage-array-based replication), a growing trend is toward applying virtualization technologies for data-migration purposes.

Virtualization appliances than sit in the SAN or LAN are one category of the new breed of data-migration tools that are quietly finding a place in environments where data migration is a regularly occurring activity. They can be leveraged to enable transparent data movement without affecting server data access. As a result, service outages are significantly shortened, with downtime only needed for the mounting, cutover and validation of the new storage targets.

Product options exist for both block-based SAN and file-oriented network-attached storage (NAS). Among the sampling of SAN migration appliances are IBM's SAN Volume Controller, FalconStor Software's IPstor and Brocade Communications Systems' Data Migration Manager. In the NAS world, EMC's Rainfinity and F5 Networks/Acopia Networks' ARX are file system virtualization platforms that can be leveraged as migration appliances.

An advantage of appliance-type devices is that they can be introduced temporarily to perform migration tasks and then removed, but other storage virtualization options also offer migration capabilities if they are present in the environment. The controller-based Universal Storage Platform is a very popular data-migration option in Hitachi Data Systems environments, and switch-based options are available from Incipient Inc., Cisco Systems and EMC.

Introducing virtualization technology for data migration represents a reasonable waypoint on the path to more wide-ranging adoption of storage virtualization. It provides a practical means to attain a comfort level with the technology before an organization is ready to fully embrace it, and, at the same time, alleviates some of the challenges associated with an often difficult task.