Media-error risk management
A bad-sector warning is not something to clear and forget. It is evidence that portions of a spinning disk cannot be used reliably, and the risk changes when the count is increasing, the pool is degraded, or other drives in the same array are aging. Synology’s current SMART guidance treats bad-sector information as part of drive-health monitoring, while NVMe SSDs follow a different health mechanism.
Quick answer
Back up before trying to prove how bad the drive is
If the disk contains unique data or participates in a pool whose redundancy is already reduced, establish a verified copy first. Diagnostic confidence is useful, but data survival is the objective.
Current Amazon listings
Replacement and migration DiskStation options
Product cards are supporting purchase references only; they do not determine whether your failed drives are recoverable or whether a specific migration pairing is supported.
Technical decision
One bad-sector number matters less than the direction of travel
A stable small count and a count that grows between checks are different situations. Growth, I/O errors, reconnections or a failed self-test strengthen the case for prompt replacement.
Interactive recovery tool
Drive Health Risk Checker
This tool routes the symptoms you select to a safer next step. It does not issue destructive commands. Before initializing a disk, deleting a pool, reinstalling DSM or moving the only copy of important data, verify the exact live Synology procedure for your model and DSM build.
Recovery safety checklist
Four rules before you change a failing Synology system
Preserve readable data first
If unique files can still be opened, copy or back them up before changing storage metadata, reinstalling DSM or running stressful diagnostics.
Record drives and bays
Capture drive serial numbers, bay positions, health states and DSM messages before swapping disks or moving them to another chassis.
Match the action to the failure layer
A degraded pool, crashed volume, failed system partition, bad drive and failed bay have different supported recovery paths.
Keep a rollback path
During migration or recovery, do not erase the source system until the destination data, permissions, applications and backups have been verified.
Bad sectors are a media symptom
On HDDs, bad sectors represent areas the drive cannot reliably use. The drive may remap some failures internally, but DSM warnings should be treated as evidence of aging or damage rather than a cosmetic alert.
For a bad-sector alert, bad sectors are a media symptom should be evaluated as part of a time series rather than a one-time number. Record the count, drive serial, temperature and date, then compare later observations only if the array is safe enough to keep operating. A rising value, additional read errors or reduced RAID redundancy pushes the decision toward replacement more quickly. This checkpoint should therefore protect against the common mistake of waiting for a hard failure merely because the NAS still serves files today.
Growth is more important than a single snapshot
Record the count and time. If the number rises over hours or days, the media is actively deteriorating. A flat count does not guarantee safety, but a rising count materially increases replacement urgency.
For a bad-sector alert, growth is more important than a single snapshot should be evaluated as part of a time series rather than a one-time number. Record the count, drive serial, temperature and date, then compare later observations only if the array is safe enough to keep operating. A rising value, additional read errors or reduced RAID redundancy pushes the decision toward replacement more quickly. This checkpoint should therefore protect against the common mistake of waiting for a hard failure merely because the NAS still serves files today.
Pool redundancy changes the acceptable delay
A healthy SHR-1 or RAID 5 pool has one level of tolerance; a degraded pool waiting for rebuild has much less. A questionable second disk during a rebuild can turn a routine replacement into data loss.
For a bad-sector alert, pool redundancy changes the acceptable delay should be evaluated as part of a time series rather than a one-time number. Record the count, drive serial, temperature and date, then compare later observations only if the array is safe enough to keep operating. A rising value, additional read errors or reduced RAID redundancy pushes the decision toward replacement more quickly. This checkpoint should therefore protect against the common mistake of waiting for a hard failure merely because the NAS still serves files today.
Backups should be verified before heavy testing
Extended health tests and scrubbing create sustained I/O. When a drive is already reporting media problems, first verify that critical data can be restored elsewhere, then schedule deeper diagnostics if they still add value.
For a bad-sector alert, backups should be verified before heavy testing should be evaluated as part of a time series rather than a one-time number. Record the count, drive serial, temperature and date, then compare later observations only if the array is safe enough to keep operating. A rising value, additional read errors or reduced RAID redundancy pushes the decision toward replacement more quickly. This checkpoint should therefore protect against the common mistake of waiting for a hard failure merely because the NAS still serves files today.
SMART status adds context but is not the whole story
An Attention Required or failing test supports replacement, yet a Normal result does not cancel a growing bad-sector count or repeated read errors. Treat all the evidence together.
For a bad-sector alert, smart status adds context but is not the whole story should be evaluated as part of a time series rather than a one-time number. Record the count, drive serial, temperature and date, then compare later observations only if the array is safe enough to keep operating. A rising value, additional read errors or reduced RAID redundancy pushes the decision toward replacement more quickly. This checkpoint should therefore protect against the common mistake of waiting for a hard failure merely because the NAS still serves files today.
Temperature and vibration can worsen weak media
Excess heat, poor cooling and mechanical vibration increase stress on spinning disks. Confirm fans and airflow are normal so that a replacement drive is not installed into the same environmental problem.
For a bad-sector alert, temperature and vibration can worsen weak media should be evaluated as part of a time series rather than a one-time number. Record the count, drive serial, temperature and date, then compare later observations only if the array is safe enough to keep operating. A rising value, additional read errors or reduced RAID redundancy pushes the decision toward replacement more quickly. This checkpoint should therefore protect against the common mistake of waiting for a hard failure merely because the NAS still serves files today.
Do not rebuild onto another suspect member
Before replacing one failed disk, inspect the remaining array members. If several peers have growing media errors or are the same age, plan the rebuild with awareness that the surviving disks will face heavy reads.
For a bad-sector alert, do not rebuild onto another suspect member should be evaluated as part of a time series rather than a one-time number. Record the count, drive serial, temperature and date, then compare later observations only if the array is safe enough to keep operating. A rising value, additional read errors or reduced RAID redundancy pushes the decision toward replacement more quickly. This checkpoint should therefore protect against the common mistake of waiting for a hard failure merely because the NAS still serves files today.
Replacement capacity must satisfy the array
Choose a compatible disk that meets the pool’s minimum size. Nominal capacity labels can hide slightly different byte counts, so use Synology guidance rather than assuming every drive sold as the same terabyte size is interchangeable.
For a bad-sector alert, replacement capacity must satisfy the array should be evaluated as part of a time series rather than a one-time number. Record the count, drive serial, temperature and date, then compare later observations only if the array is safe enough to keep operating. A rising value, additional read errors or reduced RAID redundancy pushes the decision toward replacement more quickly. This checkpoint should therefore protect against the common mistake of waiting for a hard failure merely because the NAS still serves files today.
A warranty claim is separate from data protection
A vendor may replace a defective drive, but warranty service does not recover the files. Secure the data and array first; pursue warranty replacement after the storage is stable.
For a bad-sector alert, a warranty claim is separate from data protection should be evaluated as part of a time series rather than a one-time number. Record the count, drive serial, temperature and date, then compare later observations only if the array is safe enough to keep operating. A rising value, additional read errors or reduced RAID redundancy pushes the decision toward replacement more quickly. This checkpoint should therefore protect against the common mistake of waiting for a hard failure merely because the NAS still serves files today.
NVMe health does not use the same warning path
Synology notes that NVMe SSDs use built-in monitoring and do not present the same bad-sector warning mechanism. SSD wear and media errors should be interpreted through the NVMe health information instead.
For a bad-sector alert, nvme health does not use the same warning path should be evaluated as part of a time series rather than a one-time number. Record the count, drive serial, temperature and date, then compare later observations only if the array is safe enough to keep operating. A rising value, additional read errors or reduced RAID redundancy pushes the decision toward replacement more quickly. This checkpoint should therefore protect against the common mistake of waiting for a hard failure merely because the NAS still serves files today.
After replacement, monitor the rebuild and new disk
Watch Storage Manager during repair, confirm the new drive remains healthy and avoid unnecessary workload while redundancy is being restored. A completed rebuild should be followed by backup verification.
For a bad-sector alert, after replacement, monitor the rebuild and new disk should be evaluated as part of a time series rather than a one-time number. Record the count, drive serial, temperature and date, then compare later observations only if the array is safe enough to keep operating. A rising value, additional read errors or reduced RAID redundancy pushes the decision toward replacement more quickly. This checkpoint should therefore protect against the common mistake of waiting for a hard failure merely because the NAS still serves files today.
Repeated warnings justify a lifecycle decision
If the NAS has several same-age disks showing warning signs, replacing one at a time may prolong risk and downtime. Compare staggered replacement with migrating the dataset to a fresh drive set and current chassis.
For a bad-sector alert, repeated warnings justify a lifecycle decision should be evaluated as part of a time series rather than a one-time number. Record the count, drive serial, temperature and date, then compare later observations only if the array is safe enough to keep operating. A rising value, additional read errors or reduced RAID redundancy pushes the decision toward replacement more quickly. This checkpoint should therefore protect against the common mistake of waiting for a hard failure merely because the NAS still serves files today.
Questions people ask
Synology Bad Sector Warning questions
How serious is a Synology bad-sector warning?
It is a real drive-health signal. Urgency increases when the count grows, the array is degraded, or other I/O errors appear.
Bad-sector questions are risk questions: trend, redundancy and backup status matter more than the comforting fact that the drive still spins.
Should I replace a drive with bad sectors?
Replacement is prudent when the count grows or other health evidence is abnormal. Protect data before waiting for a hard failure.
Can bad sectors be repaired?
A drive may remap failing sectors internally, but you should not rely on that as a permanent repair for important storage.
Should I run an extended SMART test?
Only after considering the backup and pool state. Long tests add stress and may be the wrong first step during an active failure.
Can data scrubbing fix bad sectors?
Scrubbing can detect and correct certain redundancy inconsistencies, but it does not make physically failing media healthy.
Does one bad sector mean immediate failure?
Not necessarily, but the trend matters. A growing count is a much stronger replacement signal than one stable historical event.
Can I keep using the NAS during rebuild?
DSM may allow access, but reducing unnecessary workload during repair can lower stress while redundancy is being restored.
Are SSD bad sectors the same?
NVMe SSDs use a different health-monitoring path in Synology DSM. Interpret their health and wear indicators rather than applying the HDD warning model directly.
Should I replace other same-age drives too?
Inspect them carefully. A second weak disk during rebuild is a major risk, so same-age peers with warnings may justify a broader refresh plan.
Will warranty replace my data?
No. Drive warranty covers hardware according to the vendor's terms; it is not a data-recovery service.
Official references and methodology
Verify the live DSM state before any destructive recovery step
This bad-sector guide treats sector growth as a trend to investigate, not an invitation to keep stress-testing a marginal disk. The workflow compares warning history, SMART results, I/O errors, pool state and backup freshness before deciding whether to monitor or replace. Because media errors can worsen during rebuild activity, the safest order is to secure recoverable data before forcing additional work onto a suspect drive.
- Synology: S.M.A.R.T. test FAQ
- Synology: Repair a storage pool
- Synology: Determine whether errors come from the drive or slot
As an Amazon Associate, Cloudzat may earn from qualifying purchases. Failure states, DSM behavior, migration compatibility and recovery options can change by model and DSM build. Preserve readable data and verify Synology's current Knowledge Center instructions before initializing drives, deleting pools, reinstalling DSM or changing the only copy of important data.