Synology NAS Error Code 28: How to Fix It

Medium 2-48 hours (backup and S.M.A.R.T. test can take hours; RAID rebuild can take up to 24+ hours) Medium Severity Verified June 2026
Summarize with ChatGPTSummarize with ClaudeSummarize with Perplexity Add as Preferred Source on Google
Error Code
28
Brand
Synology
Product Type
nas
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
2-48 hours (backup and S.M.A.R.T. test can take hours; RAID rebuild can take up to 24+ hours)
Synology NAS Error Code 28 is triggered when DSM detects that one or more hard drives in your NAS have a high reallocated sector count, a S.M.A.R.T. health indicator that signals the drive is remapping bad sectors to spare areas. This is a medium-severity warning that means your drive is compensating for physical damage or wear, and while it may still function, continued use without action risks data loss. Acting quickly to back up your data and assess the drive's health is essential.
Ad

Tools You'll Need

How to Fix Error Code 28

  1. Log In to Synology DSM and Identify the Affected Drive

    Do NOT power off or remove the drive yet. Sudden removal can disrupt an active RAID volume and cause additional data loss.

  2. Run a S.M.A.R.T. Extended Test on the Drive

    Do not interrupt the S.M.A.R.T. test once it has started, as this can cause incomplete results and may stress a compromised drive further.

  3. Back Up All Critical Data Immediately

    If your NAS volume is already in a degraded RAID state, perform the backup before making any changes to the storage pool or RAID array.

  4. Check the Storage Pool and Volume Health

  5. Check Drive Firmware and Update DSM

    Always back up data before applying firmware updates to a hard drive, as the update process carries a small risk of failure.

  6. Replace the Failing Drive if S.M.A.R.T. Confirms Degradation

    Always power off the NAS completely before physically removing a drive, unless your specific NAS model supports hot-swapping and you have confirmed this in the hardware manual. Handle drives gently to avoid further damage.

  7. Rebuild the RAID Array with the New Drive

    During RAID rebuild, NAS performance will be reduced. Avoid heavy read/write activity during this period, as other drives are under increased stress and a second drive failure during rebuild would result in data loss.

  8. Enable Automatic S.M.A.R.T. Scheduled Tests Going Forward

Parts You May Need

NAS hard drive (3.5-inch or 2.5-inch depending on NAS model)
Check Price on Amazon
External USB hard drive or NAS-compatible external storage
Check Price on Amazon
NAS hard drive (3.5-inch or 2.5-inch depending on NAS model)
Check Price on Amazon
External USB hard drive or NAS-compatible external storage
Check Price on Amazon
NAS hard drive (3.5-inch or 2.5-inch depending on NAS model)
Check Price on Amazon
External USB hard drive or NAS-compatible external storage
Check Price on Amazon
Ad

When to Call a Professional

Contact Synology support or a data recovery professional if: (1) your NAS volume has already failed and you cannot access your data, (2) multiple drives are showing S.M.A.R.T. failures simultaneously, (3) you do not have a backup and need to recover data from a failing drive before replacing it, or (4) you are uncomfortable physically handling drives or interpreting S.M.A.R.T. data. A professional data recovery service is essential if the drive has mechanically failed and contains irreplaceable data, as DIY recovery attempts on a failing drive can cause permanent data loss.

Frequently Asked Questions

What does a high reallocated sector count mean on a Synology NAS?
Reallocated sectors are areas of a hard drive that the drive's firmware has identified as damaged or unreliable and remapped to spare sectors on the drive. A high reallocated sector count (S.M.A.R.T. Attribute 5) means the drive has accumulated significant physical damage over time. While the drive may still work, a rising count is a strong indicator of impending drive failure and should be taken seriously.
Is Error Code 28 on Synology NAS urgent?
Error Code 28 is medium severity but should be treated as urgent in terms of data protection. Back up your data immediately. The drive may continue working for days, weeks, or fail without further warning. The sooner you back up and plan a drive replacement, the lower your risk of data loss.
Can I fix a drive with high reallocated sectors without replacing it?
You cannot reverse physical damage that has already caused sectors to be reallocated. Running a full disk format or a manufacturer's diagnostic tool may help identify the extent of the problem, but the underlying physical degradation cannot be repaired through software. If the count is rising or the S.M.A.R.T. test reports failures, drive replacement is the only reliable fix.
Will I lose data when replacing a drive in my Synology NAS?
If your NAS uses a redundant RAID configuration (such as RAID 1, RAID 5, RAID 6, or SHR with redundancy) and only one drive has failed, you should be able to replace the drive and rebuild the array without data loss. However, this is only safe if all remaining drives in the pool are healthy. Always back up your data first before replacing any drive, as rebuilding a degraded RAID array puts stress on the remaining drives.
How do I check which drive is causing Error Code 28 in Synology DSM?
Log into DSM and navigate to Storage Manager > HDD/SSD. Each drive will be listed by bay number (Disk 1, Disk 2, etc.) along with its health status. Drives flagged as 'Caution' or 'Failed' are the ones with issues. Click on the flagged drive and select 'Health Info,' then go to the S.M.A.R.T. tab to see the specific attribute values, including the reallocated sector count (Attribute 5).

Related Error Codes