What are bad sectors?
Bad sectors are areas on a hard drive or SSD that can no longer reliably store data due to physical damage or manufacturing defects. When your computer tries to read or write data to a bad sector, it may result in data loss or corruption. Bad sectors often start out as weak or marginal sectors before progressing to full failure.
Can SSDs develop bad sectors?
Yes, SSDs can absolutely develop bad sectors like traditional hard disk drives (HDDs). In fact, some of the same causes of bad sectors apply to both SSDs and HDDs:
- Physical damage from impacts or drops
- Electrical damage from power surges/spikes
- Manufacturing defects in NAND flash memory chips or other components
- Wear and tear over time as cells degrade from repeated write/erase cycles
The NAND flash memory in SSDs wears out after a certain number of write/erase cycles, which can lead to bad sectors. Consumer SSDs are typically rated for anywhere from a few hundred to a few thousand write/erase cycles before cells begin to degrade.
How can I check for bad sectors on an SSD?
There are a few methods to scan for and detect bad sectors on an SSD:
- Use the CHKDSK utility in Windows to scan the drive and check for bad sectors. CHKDSK will attempt to repair any found.
- Use the S.M.A.R.T. (Self-Monitoring, Analysis and Reporting Technology) monitoring capabilities built into the SSD. S.M.A.R.T. keeps track of drive errors and performance to predict failures.
- Use the drive manufacturer’s utility software, which often includes bad sector scanning and repair tools.
- Use third-party disk diagnostic utilities like Hard Disk Sentinel or HDD Scan to do more in-depth bad sector detection.
Checking SMART attributes like “Reallocated Sectors Count” or “Uncorrectable Sector Count” can indicate the presence of bad sectors that have been remapped.
What happens when an SSD has bad sectors?
The main consequence of bad sectors on an SSD is data loss, corruption, and inaccessibility. Because the cells in a bad sector can no longer reliably store data, any attempt to read or write data to them may fail. The data may appear corrupted or be entirely unreadable.
The SSD’s controller will detect when a sector goes bad. When this happens, it will remap the bad sector to spare good cells set aside for this purpose. This remapping is transparent to the operating system. However, if many bad sectors accumulate, the spare capacity may exhaust. At that point, data loss is likely.
Performance will also degrade as more bad sectors accumulate and the drive allocates more time toward error correction and remapping. The presence of bad sectors may indicate the SSD is nearing the end of its usable life.
Can I continue using an SSD with bad sectors?
You can potentially continue using an SSD with some bad sectors, but with caution:
- Monitor S.M.A.R.T. attributes closely for any deteriorating conditions.
- Be prepared to migrate data off the drive if the bad sector count increases rapidly.
- Make frequent backups to protect important data against sudden failure.
- Avoid writing critical data that cannot be afford to lose to the drive.
- Consider replacing the SSD if bad sectors accumulate rapidly or performance drops.
While an SSD can continue working with some remapped bad sectors, the risk of unrecoverable data loss goes up over time. It’s not recommended for crucial data storage or applications requiring high reliability.
Can bad sectors on an SSD be repaired or fixed?
Unfortunately, there is no way to truly repair or fix bad sectors that have developed on an SSD. The damage to the physical NAND flash memory cells is permanent. Remapping the sectors is the best that can be done.
Some tools may claim to repair bad sectors, but this is really just remapping them rather than correcting the underlying damage. The total number of spare cells is finite, so remapping constantly consumes more of this reserve.
That said, reformatting or securely erasing the SSD will trigger a full remapping of any bad areas on the drive. This provides a fresh start with all sectors initially mapped to good cells. However, any underlying physical defects will eventually redevelop.
How can I extend the life of an SSD and minimize bad sectors?
You can help minimize SSD bad sectors by:
- Following the manufacturer’s guidelines for use, storage, and environmental conditions.
- Avoiding unexpected power loss – use a UPS if power is unreliable.
- Keeping the drive cool – ensure adequate airflow and heatsinking.
- Not maxing out drive writes – stay below the rated TBW capacity.
- Letting the controller spread writes across cells via wear leveling.
- Running regular S.M.A.R.T. checks and short drive self-tests.
- Upgrading drive firmware when the manufacturer releases updates.
While SSD lifespans are limited, taking care of the drive and managing writes can help extend useful service life before bad sectors become a problem.
What causes bad sectors on an SSD?
Typical causes of bad sectors developing on SSDs include:
- Early onset of write/erase cycle degradation of NAND flash memory cells. This can be accelerated by very high write workloads.
- Read disturbs which can corrupt cells by repeatedly accessing neighboring cells.
- Write disturbs that corrupt cells via writes to other locations.
- Overheating which accelerates all forms of NAND degradation.
- Physical damage from drops, shocks, vibrations that break down insulating layers and destroy function.
- Manufacturing defects present since the drive’s production but not detected until later in service life.
- Power surges or power failures during write operations that corrupt data in process.
- Controller errors that incorrectly map data resulting in damage via false writes.
Wear and tear or suboptimal operating conditions are the most common factors in the development of bad sectors. But they can also arise unexpectedly from hardware flaws or external electrical issues.
Are a few bad sectors normal on older SSDs?
As an SSD ages and endures more write/erase cycles, it is considered normal to develop some quantity of bad sectors. This is the inevitable result of NAND flash memory wearing out over time.
A small number of remapped sectors may not indicate any serious problems on an older SSD. However, the threshold for what is considered normal or acceptable can vary by factors like:
- Total age and cumulative data written to the SSD.
- Rated lifespan and write endurance of that specific model.
- Whether the rate of new bad sectors is accelerating or stable.
- The manufacturer’s specifications for normal rates of reallocated sectors.
For example, on an older SSD rated for 5,000 P/E cycles, a few hundred reallocated sectors may be perfectly typical after several years of moderate use. But on a newer drive rated for 10 times as many cycles, it could indicate premature wear.
Can SSDs fail completely due to bad sectors?
Excessive bad sectors can definitely cause complete SSD failure. When the collected bad sectors surpass the spare capacity to remap them, the SSD will have no choice but to mark certain areas as unrecoverable errors.
At that point, data loss becomes severe because writes simply cannot be committed reliably to the NAND flash memory. The SSD will be forced into a read-only state to avoid further damage. If the SSD also cannot successfully read data without extensive error correction, it may become completely non-functional.
The SSD failure rate rises rapidly in later years as wear leveling exhausts its capabilities and bad sectors accumulate. However, gradual failure is more likely than sudden total failure in most cases. S.M.A.R.T. warnings and performance decline first indicate significant issues.
Can I repair bad sectors myself?
There is no DIY method to truly repair bad sectors on an SSD. The NAND memory and other hardware cannot be meaningfully accessed or replaced by consumers. The SSD must be treated as a sealed unit.
However, you can indirectly remap sectors by doing a secure erase. This will force a fresh mapping of all flash cells, letting the SSD controller retest the drive and allocate spare cells as needed to wall off bad areas. This can return an SSD with some bad sectors to normal function, but only temporarily.
If the media has substantial damage or wear, bad sectors will quickly return. In these cases, a professional SSD recovery service may be able to swap chip-level components to salvage the drive. But this is expensive and not guaranteed.
Should I replace my SSD if I have bad sectors?
If your SSD is reporting reallocated sectors or pending sectors, you should begin planning for a replacement drive. While the SSD may keep working for a while longer, bad sectors indicate it is running on borrowed time.
Continuing to use an SSD with known bad sectors risks permanent data loss when the cells fail entirely. The most prudent option is to retire it from important duties, begin migrating data to a new SSD, and watch for any rapid deterioration.
An SSD used for non-critical purposes like gaming or scratch storage may continue providing utility even with some bad sectors. But for reliable storage you cannot afford to lose, replacement is advised once sectors go bad.
Can bad sectors spread or increase on an SSD?
Unfortunately, the accumulation of bad sectors is likely to accelerate once significant numbers appear on an SSD. Here are some reasons bad sectors tend to breed more bad sectors:
- Whatever wear and tear caused the initial bad sectors will continue degrading cells across the NAND flash memory.
- Remapping bad sectors consumes some of the finite spare capacity to absorb future failures.
- As performance decreases, write operations take longer and cells are more likely to be corrupted.
- With less reliable cells, the SSD controller may make more mistakes mapping data that causes damage.
While SSD controllers are optimized to isolate and work around initial bad sector emergence, their resilience declines once multiple failures occur. The risk of unrecoverable read/write errors then grows rapidly.
Will a secure erase fix bad sectors on an SSD?
Performing a secure erase on an SSD will effectively remap all existing bad sectors. By resetting all cells to a clean slate, the SSD controller can redistribute spare cells and mask existing failed ones.
However, a secure erase cannot repair the underlying physical damage causing bad sectors. Any defective NAND flash memory cells will eventually degrade again. The bad sectors are likely to reappear after more writes, even if the drive appears normal initially after securing erasing.
The only exception is if bad sectors arise due to mapping mistakes or software issues that get cleared by a reset. Then a secure erase may provide a permanent fix. But for hardware-level cell wear, bad sectors will return despite remapping because the damage remains.
Can SSD bad sectors become good sectors again?
Remapped bad sectors generally do not revert to being good sectors again after reallocation. The original physical cell damage causing them to go bad remains. The cells are essentially permanently retired from use due to wear or defects.
That said, a few scenarios can make bad sectors temporarily test good again on SSDs:
- If failures arise from marginal electrical issues, cells may pass initial integrity scans after being left unused.
- A firmware update or controller reset could clear historical flags marking certain cells as bad.
- During intense activity, the controller may have conservatively reallocated cells proactively but they are still functional.
These cases represent SSD mapping issues rather than physical defects, so a brief return to normal function is possible. But true irreversible NAND flash degradation that made a sector go bad in the first place will not improve.
Can SSD controllers detect and remap all bad sectors?
Modern SSD controllers are generally excellent at detecting emerging bad sectors and transparently remapping them before they impact user data. However, they may struggle to keep up with extremely high rates of new bad sectors exceeding spare area capacity.
Other limits on bad sector detection and remapping include:
- New defects arising during active file writes may escape detection until data gets corrupted.
- Poor algorithms may fail to identify marginal sectors until they fully fail.
- Resource exhaustion during intense activity periods can delay remapping actions.
- Insufficient spare cells to remap detected defects, forcing the SSD into read-only mode.
Overall, automatie bad sector management is reliable for typical failure rates. But SSDs can still be caught off guard by sudden surges of new bad sectors advancing faster than the controller can assess and contain them.
Should I be concerned about any bad sectors on a new SSD?
The presence of any detected bad sectors on a new, recently purchased SSD is concerning and may indicate a manufacturing defect or premature failure.
While a handful of reallocated sectors are expected over the total multi-year lifespan of an SSD, a brand new drive should not have any degraded cells. Finding bad sectors out of the box likely means:
- There was an error in NAND flash chip production or integration that eluded screening.
- Physical damage occurred pre-sale – possibly a return customer re-sold as new.
- The SSD was used for testing then repackaged and resold.
If your new SSD already shows reallocated sectors, it’s reasonable to exchange it or request a refund rather than keep a flawed unit. A few bad sectors often snowball into widespread drive issues later.
Can using my SSD at full capacity cause bad sectors?
There is little direct link between filling up an SSD completely and immediately causing bad sectors. However, operating an SSD near max capacity does accelerate wear in a few indirect ways:
- The drive has less spare area to devote to over-provisioning and remaps.
- Cleaning cycles and garbage collection become less efficient.
- More frequent, smaller writes occur as remaining space runs low.
- Fragmentation increases as the controller scrambles to find free blocks.
In combination, these effects of using an SSD near full capacity cause substantially more write amplification. The higher total data writes then bring the drive closer to its rated endurance limits.
The resulting increased wear on NAND flash memory does make bad sectors more likely over time when running SSDs at high utilization. But the risks mostly arise from the longer-term amplification of writes.
Do SLC SSDs have fewer bad sectors than MLC and TLC SSDs?
SSDs using higher-quality SLC NAND flash generally have superior endurance and bad sector performance compared to drives using denser but less durable MLC and TLC NAND:
- SLC – One bit per cell. Highest performance and longevity. Typically 10x more write cycles before failure than MLC.
- MLC – Two bits per cell. Middle ground performance and endurance. Used for many consumer SSDs.
- TLC – Three bits per cell. Lower performance but greater density. Most prone to bad sectors as cells wear out.
However, progression of bad sectors follows the same general pathways regardless of NAND type. SLC SSDs simply take far longer to reach the substantial bad sector counts that force TLC drives to end-of-life. But once cell wear progresses far enough, all types of NAND will develop bad sectors.
Can bad sectors spread between drives in RAID arrays?
Bad sectors on one drive within a RAID array will not directly spread to other drives and cause their sectors to also fail. The physical failures within NAND chips are isolated. However, multiple drives failing together can often originate from a shared cause:
- If vibrations or impulse damage affected one drive, others may be affected too.
- Drives purchased and installed together will have similar mileage and wear.
- Environmental factors like heat or power delivery impact all drives.
- A controller or connection issue could corrupt data on one drive then get propagated to others.
So while the bad sectors themselves remain independent, related circumstances can lead to one drive’s failure unmasking or accelerating wear issues on other drives within the array.
Conclusion
While SSDs can technically continue operating with some bad sectors by remapping those areas, the risk of data loss and continued performance decline significantly increases once cells begin to permanently fail. Some bad sectors may be inevitable as SSDs wear out, but allowing them to accumulate in number rather than replacing the drive is unwise for any application requiring reliable storage. Monitoring tools can provide early warnings if reallocated sectors start to increase at an abnormal rate.