Symptom
After a Battery Backup Unit (BBU) failure, the write speeds have significantly decreased.
Diagnosis
When a BBU failure occurs, you may observe the following events:
- Error 0x21042507: Battery Backup Unit (BBU) error detected (reported by slot A).
- Information 0x02011201: Due to the event condition, the controller’s write policy was forced into write-through mode (reported by slot A).
Cause
The performance drop occurs because the system automatically switches to write-through mode to ensure data integrity when a BBU failure is detected. This behavior is part of the system’s safety mechanism.
Solution
- Replace the Failed BBU
Ensure the failed BBU is replaced with a functioning unit. - Wait for BBU Status to Normalize
Do not manually switch the write policy back to "Write-back" mode until the BBU status is confirmed as normal. Switching prematurely may risk data integrity. - Switch Back to Write-back Mode
After the BBU status is confirmed normal via EonOne, change the write policy back to "Write-back" mode to restore optimal performance.
By following these steps, you can safely restore the system’s performance while maintaining data protection.