Repair of the local drives does not require an Oracle Exadata Database Machine database server to be shut down.

No downtime of the rack is required, however the individual server may require downtime, temporarily taking it out of the cluster.

• Verifying the Database Server Configuration
  Oracle recommends verifying the status of the database server RAID devices to avoid possible performance impact, or an outage.
• Monitoring a Database Server RAID Set Rebuilding
  
• Reclaiming a Hot Spare Drive After Upgrading to Oracle Exadata System Software Release 12.1.2.1.0 or Later
  
• Understanding Automated Maintenance Tasks and Policies
  The Management Server (MS) performs automated maintenance tasks on the metric repository and various file systems.