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Planning. The most important consideration for any migration is the overall business impact and, specifically, the impact on an application and its ability to access data. For this reason, the planning phase is the most critical. In a large migration project, the planning phase can and should consume more staff hours than the actual migration itself.
It's important to understand where data migration fits within the larger project. Is this a data center relocation where data may have to be migrated over long distances? Part of a consolidation effort focused on maximizing storage layout for efficiency while still ensuring appropriate service levels? Or is this a lease expiration or technology refresh involving migration of data from one generation of storage hardware to the next? Data migration can also be part of a performance optimization or tiered data effort.
The heterogeneity of the environment, in terms of servers and storage, has a significant impact on the migration process, particularly in determining the numbers and types of tools available to perform the movement. Likewise, the scale of the migration in terms of numbers of hosts impacted and the volume of data to be relocated are critical factors affecting how the migration is accomplished.
Minimizing business and application impact usually translates into ensuring the smallest outage and the least performance degradation, so a key element of the planning effort is determining how to minimize migration time. This often involves organizing interdependent apps into move groups that will be migrated together.
Another key part of planning is the verification and validation process. What steps will be taken to ensure that each phase of the migration has succeeded? It's equally important to plan (and test) the fallback process.
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