Bad sectors are a common phenomenon for HDDs.¹ As long as the increase in the Bad sector count is not drastic, there should be no cause for concern. When a drive has bad sectors, some of the following symptoms may appear:

• The Bad sector count shows a value other than 0.
  1. Go to Storage Manager > HDD/SSD.
  2. Select the suspected failed drive.
  3. Click Health Info and go to History > Key Information of Drives.
  4. Check the Bad sector count graph.
• The system sends you bad sector warnings.
  1. Check your email or the DSM desktop notifications.
  2. Look for the Number of bad sectors increased or similar alerts.

DSM 6.2 to 7.2¹

Run data scrubbing periodically

Data scrubbing is a data maintenance feature that amends data in storage pools that are incorrect or incomplete. We recommend performing data scrubbing twice a year to ensure data consistency and avoid data loss in the event of a drive failure.

Check the bad sector count graph

Monitor whether the bad sector count is increasing.

1. Go to Storage Manager > HDD/SSD.
2. Select the suspected failed drive.
3. Click Health Info and go to History > Key Information of Drives.
4. Check the Bad sector count graph.
   1. If the count is stable, it is possible that the bad sectors have been corrected. Keep monitoring the drive.
   2. If the count is increasing rapidly, the drive may fail in the future. We suggest replacing it if it enters Critical status. You can refer to the Replace the defective drive section for more information.

Replace the defective drive

Check the Synology Products Compatibility List to ensure the replacement drive is compatible with your Synology NAS model.

For RAID types without data protection:

1. Back up all your data. (Tutorial)
2. Power off your Synology NAS.
3. Remove and replace the defective drive.²
4. Power on your Synology NAS.
   • Install DSM if your Synology NAS is a one-bay model. (Tutorial)
5. Create a new storage pool and volume.
6. Restore the backed up data to the storage pool and volume. (Tutorial)

For RAID types with data protection:

Remove and replace the defective drive.²

• If your Synology NAS has at least one unused drive and its DSM version is DSM 7, use the Replace Drive feature.
• If your Synology NAS does not have any unused drives or if its DSM version is older than DSM 7, replace the defective drive one at a time and repair the storage pool (DSM 7 / DSM 6.2) after each replacement.