Below are the detailed steps to replace a failed hard drive for each RAID level:

General Preparation

Identify the Failed Drive:

• Use RAID controller logs or monitoring software to confirm which drive has failed.
• Physically locate the failed drive using the drive status LEDs (if available).

Check for Backups:

• Verify a recent and complete backup exists for RAID 0, 1, 5, or 6. Backups are critical, especially for RAID 0, where data is typically unrecoverable after a failure.

Power Down or Confirm Hot-Swap Capability:

• For systems without hot-swap capability, power down the machine before replacing the drive.
• If hot-swapping is supported, ensure the RAID controller allows drive replacement while the system is running.

RAID 0: No Fault Tolerance

Steps:

Understand the Data Loss:

• RAID 0 offers no redundancy. If a drive fails, the entire array is lost. Recovery is possible only with specialized recovery tools if partial data can be salvaged.

Replace the Failed Drive:

• Physically replace the failed drive with a new drive of equal or greater capacity.

Recreate the Array:

• Use the RAID controller to recreate the RAID 0 array. This will delete all data.

Restore from Backup:

• Restore data from a backup to the newly created RAID 0 array.

RAID 1: Mirroring

Steps:

Replace the Failed Drive:

• Remove the failed drive and insert a new drive of equal or greater capacity.

Allow Automatic Rebuild:

• Most RAID 1 arrays will automatically rebuild the data onto the new drive.
• Monitor the rebuild process via the RAID controller interface or software.

Verify the Rebuild:

• Once the rebuild is complete, verify data integrity by accessing files.

RAID 5: Single Drive Redundancy

Steps:

Replace the Failed Drive:

• Remove the failed drive and insert a new drive of equal or greater capacity.

Start Rebuild Process:

• The RAID controller should detect the new drive and begin the rebuild process automatically.
• If it does not, manually start the rebuild through the RAID management interface.

Monitor the Rebuild:

• Rebuilding can take several hours or more, depending on the array size and system workload.
• Avoid heavy read/write operations during the rebuild to prevent additional stress on the remaining drives.

Verify the Array:

• Once the rebuild is complete, confirm the RAID status is healthy in the RAID management interface.

RAID 6: Dual Drive Redundancy

Steps:

Replace the Failed Drive(s):

• Remove one failed drive at a time and replace it with a new drive of equal or greater capacity.
• If both drives have failed, repeat this process for the second failed drive after the first rebuild completes.

Start Rebuild Process:

• The RAID controller will typically detect the new drive and start the rebuild process automatically.
• If not, initiate the rebuild manually through the RAID management interface.

Monitor the Rebuild(s):

• The rebuild process may take even longer in RAID 6 due to the added parity calculations.
• Replace the second failed drive after the first rebuild completes to ensure the array remains stable during the process.

Verify the Array:

• Once the rebuild is complete, check the RAID controller or management interface to confirm the array's status is healthy.

After Replacing Drives

Update Firmware:

• Check if your RAID controller or drives require firmware updates to prevent future issues.

Perform Diagnostics:

• Run SMART tests or other diagnostic tools to verify the health of all drives in the array.

Enable Alerts:

• Configure email or system alerts for RAID health monitoring to prevent unnoticed failures.

Critical Notes

• RAID 0: No data protection—always maintain backups. Recovery requires rebuilding from scratch after replacing the failed drive.
• RAID 1: Simple process, as data is mirrored. Replacement is straightforward.
• RAID 5 and 6: Always monitor for rebuild failures. Running degraded for long periods risks total data loss.