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Data migration: Preparation equals success

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Typical data migration challenges

Help desk support
Arrange help desk support depending on the complexity of the migration. Provide help desk staffers with appropriate details so they can field calls related to the migration. For example, if the migration is between a Unix box and a Network Appliance box, path names

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will change and users will need to remap their shares. Another example would be migrating shares of Mac users. Macs will require special handing and, in some cases, special software, such as DAVE, to ensure transferred files will be readable. These types of variations or complexities should be clearly conveyed to the help desk.

Checklist and tools Migration and test plans should address:

  • Method of migration, such as mirroring or copying
  • Details of the premigration, migration and post-migration steps
  • Required testing scripts
  • Back-out plans

There are many tools that can help ease the migration process (see "Network-based migration tools" at http://storagemagazine.techtarget.com/networkbasedmig and "Host-based migration tools" at http://storagemagazine.techtarget.com/hostbasedmig). Most data migrations are conducted using host-based tools in an offline/manual mode because this method reduces the risk of losing data. For the majority of migrations, native commands such as "ddcopy" and "xcopy," or the mirroring capabilities of the storage platforms, work well. Some migrations may even be performed using a backup and restore approach. These approaches have the advantage of not requiring any additional software, hardware or new skills.

Premigration steps
Once general planning is complete, it's necessary to determine if any upgrades or patches are required to support the migration. If you have a robust change control or configuration management program, this information may already be available. However, information should be reviewed to minimize the chance of glitches arising during the migration. Check the HBAs, switches, source and target platforms, and operating system to ensure that these are at the right version to support the migration and ongoing operations (see Checklist of migration activities).

Once the required updates have been determined, correct any items that need updating. Firmware versions, while good enough for operations, will often require updating to support the migration. Upgrades may require a system shutdown, so all business users should be notified so they can plan accordingly. It's also recommended to have a few days between the premigration shutdown and the migration to allow for troubleshooting. This waiting period helps systems to stabilize and provides you with the time to resolve any issues that arise as a result of the hardware/software upgrades before the actual migration. The waiting period will vary, but three to seven days is recommended.

The migration steps must address the appropriate level of detail based on the criticality of the data. In particular, attention must be paid to data controlled by one or more regulatory requirements. In some instances, documenting the migration at a high level will be sufficient. However, with the goal of minimizing risk, it's helpful to provide enough details (and then test against these details) to reduce the number of operational questions during the migration or the need for workarounds. It's difficult to definitively state the sets of detailed tasks because each environment is different; however, when unsure, add more detail.

This was first published in September 2005

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