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.
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