# Choosing the primary physical drive of the array

When you create a RAID level-1 logical drive on an integrated RAID controller, you must specify the primary physical drive. Doing so ensures that you retain the data on the primary physical drive. In a RAID level-1 logical drive, the data on the primary physical drive is copied to the secondary physical drive (the mirror). Any data on the secondary physical drive is destroyed.

After the logical drive is created, the physical drive Properties panel reports the mirror role (primary or secondary) of each drive:

Knowing the mirror role of each physical drive can be useful in the following situations:

- Creating a logical drive with a physical drive that already contains data.
  A server has one physical drive and the operating system is installed on that physical drive. You decide that you want a RAID level-1 logical drive to achieve redundancy. When you install a second physical drive and configure the logical drive, you must specify the original physical drive as the primary physical drive so you do not destroy the data on that drive.
- During a synchronization failure.
  After the logical drive is created, a synchronization begins to create the mirror of the primary physical drive. While the synchronization is in progress, the logical drive is displayed as critical, because the mirror is not complete and the logical drive has not achieved redundancy. During the synchronization, if the primary physical drive fails, all of the data on the drive is lost because the mirror is incomplete. If the secondary physical drive fails, the data on the primary physical drive is intact and you can create the mirror using a hot-spare drive.

## More information

- Understanding RAID level-1
- Understanding logical-drive synchronization

Glossary | Contents

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