# Understanding logical-drive migration

Logical-drive migration is a powerful and flexible feature of ServeRAID controllers. You can use logical-drive migration to do the following:

- Change the RAID level of existing logical drives
- Increase array free space, so you can create additional logical drives
- Increase size of an existing logical drive

Using the ServeRAID Manager, you can migrate a logical drive while the server is running with only minor performance degradation for users during the process.

Note: To perform logical-drive migration, the following must be true:

1. No more than seven logical drives currently exist.
   During migration, ServeRAID creates one logical drive for temporary use. When migrating logical drives, you must have an extra logical drive onto which the data migrates. ServeRAID sets this logical drive to the system state and the tree object (logical drive) is grey. When migration is complete, this logical drive is removed from the tree.
2. The logical drive that you have selected to migrate must be in the okay state.
3. The logical drive cannot be configured with RAID level-00, 10, 1E0, or 50.

If a physical drive fails during a logical-drive migration and you are migrating between RAID levels other than RAID level-0, the migration will continue and complete. Then, you must replace and rebuild the failed physical drive.

Logical-drive migrations also can recover from a power failure. If power is lost to the server during a logical-drive migration, the migration will restart as soon as power is restored, and complete without data corruption.

Note: (Cluster and failover configurations only.) A logical drive will not failover while undergoing logical-drive migration.

## More information

- Things to consider when changing the RAID level
- Example: Increasing free space
- Example: Increasing logical drive size

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