# Understanding logical-drive synchronization

The purpose of synchronizing logical drives is to compute and write the parity data on the selected drives. Synchronizing a logical drive verifies that the data redundancy for the logical drive is correct.

Note: You can determine if your controller firmware supports auto-synchronization and data scrubbing by viewing the controller properties. The properties pane reports if these features are enabled or disabled.

## Using auto-synchronization

If the logical drive is attached to a controller that supports auto-synchronization, the ServeRAID Manager automatically synchronizes all new RAID level-5, 5E, 5EE, and 50 logical drives. These logical drives must be synchronized before storing data. Auto-synchronization ensures that the parity data is accurately computed. Accurate parity is critical for updating the parity when you begin to store data.

For the ServeRAID-8i controller and ServeRAID-7t controller, the ServeRAID Manager also supports auto-synchronization for RAID level-1 and 10 logical drives. During auto-synchronization, data from the primary drive is automatically copied to the mirror drive.

Depending on the controller, the ServeRAID Manager displays either a progress indicator in the status bar or a (in animation) in the Logical devices view, indicating that auto-synchronization is in progress. You can perform some actions on the controller during an auto-synchronization, such as deleting a logical drive; however, you cannot perform a logical drive migration. Also, you can turn off the server during an auto-synchronization and, when you turn on the server, the firmware will continue the auto-synchronization where it left off.

## Using manual synchronization

When you create a logical drive that is attached to a controller that does not support auto-synchronization, you will receive a warning event in the event viewer stating that you must manually synchronize the logical drive before storing data. Use "Synchronize logical drives" to manually synchronize the logical drive. You must synchronize new RAID level-5 logical drives after you create them.

Manual synchronization can be a lengthy operation. You can synchronize the logical drive immediately or schedule it for a later date and time. You can also schedule the synchronization as a recurring task. A recurring synchronization task starts at the initial start time, then runs periodically according to the given interval: the same time each day, each week, or each month. Do not turn off the server until the manual synchronization is complete.

For ServeRAID SCSI controllers, you cannot perform any other actions on the controller until the manual synchronization is completed.

## Using manual synchronization for data scrubbing

Data scrubbing is an automatic background synchronization process. Data scrubbing keeps data "fresh" by doing the following:

- (For RAID level-5, 5E, 5EE, or 50) Reading data and rewriting the data parity.
- (For RAID level-1, 1E, 10, 1E0) Reading data and rewriting the mirror data.

If data scrubbing is disabled or your controller firmware does not support data scrubbing, consider manually synchronizing your logical drives weekly. This does not alter data on the drive.

If data scrubbing is disabled on your ServeRAID controller, you can enable data scrubbing, but not through the ServeRAID Manager console. Instead, use the IPSSEND command-line program included on the IBM ServeRAID Support CD. For more information, refer to the IBM ServeRAID User's Reference.

## More information

- Synchronizing logical drives (action)
- Enabling and disabling data scrubbing (action)
- Understanding scheduled tasks
- Using the Task Manager

Glossary | Contents

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