What are bad sectors?
Bad sectors are areas on a hard disk drive (HDD) that can no longer be read from or written to due to physical damage or corruption. They occur when the drive’s read/write heads cannot access the platter surface to magnetically store or retrieve data. There are two types of bad sectors:
Physical bad sectors are areas where the platter’s magnetic coating has been physically damaged or worn off. This damage is permanent and these sectors can never be used again. Physical damage can occur from the drive experiencing a shock or the read/write heads touching the platter surface. [1]
Logical bad sectors do not have physical damage but cannot be accessed due to corruption in the sector’s data or mapping. The operating system may flag these sectors as bad if it cannot successfully read or write data. Logical bad sectors have a chance of being repaired by rewriting the sector’s data and mapping information.
The difference is that physical bad sectors are permanently damaged and unusable, while logical bad sectors may potentially be repaired and accessed again if the corruption can be fixed.
Identifying bad sectors
Some signs of a hard drive having bad sectors are the computer freezing or crashing more frequently than usual, read/write errors appearing, and programs or files taking longer than normal to load or open. Drive scanning tools can be used to specifically check for and identify bad sectors.
Windows includes the built-in chkdsk command (https://www.seagate.com/support/kb/what-do-i-do-if-my-drive-reports-bad-sectors-196351en/). Running chkdsk /f scans the drive and attempts to repair any bad sectors. Free third party tools like HDDScan, DiskCheckup, and Victoria can also be used to scan for and identify bad sectors on hard drives (https://www.micronicsindia.com/6-ways-to-test-a-hard-disk-drive-hdd-for-bad-sectors-without-opening-your-computer/). These tools report the total number and locations of any bad sectors detected.
Dangers of using drives with bad sectors
Using hard drives with bad sectors can lead to a number of issues:
Potential data loss or corruption: Bad sectors can cause files to become corrupted or unreadable. As more sectors go bad, the risk of irrecoverable data loss grows. According to this SuperUser post, bad sectors will likely keep increasing over time.
Performance issues: Drives have to work harder to read and write data around bad sectors. This can lead to slowdowns and freezing. The more bad sectors, the worse performance will become over time.
Failure to boot or load programs: Critical boot files or program files becoming corrupted due to bad sectors can prevent booting or loading programs. This may eventually lead to a complete failure of the drive.
In summary, continuing to use a drive with bad sectors puts your data at risk and will likely lead to worsening performance and potential full failure over time. It’s best to replace drives once they start showing signs of bad sectors.
Fixing bad sectors
There are a few options for trying to fix bad sectors on a hard drive:
Low-level formatting, also known as a full format, can remap bad sectors by marking them as unusable and assigning spare sectors to replace them. This process erases all data on the drive. Tools like Spinrite can perform low-level formatting and repairs.
Specialized repair tools like Spinrite can also attempt to repair sectors by recovering readable data, fixing firmware issues, and refreshing magnetic storage strength. Success depends on the extent and type of damage to the sectors.
If the bad sectors cannot be repaired, the most reliable solution is to replace the hard drive. With an accumulation of bad sectors, the drive will continue degrading until it completely fails. Replacing it before extensive data loss occurs is recommended.
Backing up important data regularly, preferably to another drive, is advisable to avoid permanent data loss when sectors go bad.
Data recovery from drives with bad sectors
Recovering data from a drive with bad sectors can be challenging, but is possible in many cases. Experts recommend taking the following steps:
First, it’s important to clone the drive before attempting any recovery. Cloning makes an identical copy of the drive, preserving the file structure and data. This protects the original drive from further damage during recovery efforts. Tools like EaseUS Disk Copy can reliably clone drives with bad sectors.
Next, use data recovery software designed specifically for drives with bad sectors. Options like Wondershare Recoverit can scan the drive, skipping bad sectors, and reconstruct files from the remaining data. This maximizes the chance of partial or full recovery.
In severe cases with mechanical damage or many bad sectors, it may require professional data recovery services. Companies like DriveSavers and Gillware can attempt specialized techniques like drive transplants and clean room recovery, but at much higher costs.
The key is to avoid further writes to the damaged drive, work from a clone, and use the right tools designed to handle drives with physical errors. With an optimal process, chances are good for recovering data from a drive with some bad sectors.
Backing up data on failing drives
It is critical to frequently back up your data when a hard drive starts developing bad sectors. Bad sectors often indicate that a hard drive is failing and may stop working entirely in the future [1]. When bad sectors are detected, immediately back up any critical data on the drive before attempting to repair it.
The best way to back up a hard drive with bad sectors is to use disk imaging software. Disk imaging creates an exact sector-by-sector copy of your entire hard drive, preserving its structure and partitions. Popular disk imaging tools include EaseUS Todo Backup, Macrium Reflect, and Clonezilla [2]. Imaging software can successfully back up drives with bad sectors that may be inaccessible to regular file copy backups.
In addition to disk images, also be sure to regularly back up important individual files and folders. Back up data to an external drive or cloud storage. Frequent backups minimize potential data loss if your hard drive fails entirely before you have a chance to replace it.
Preventing bad sectors
There are several steps you can take to help prevent bad sectors from developing on your hard drives:
Keep drive cool and protected – Hard drives generate heat during operation which can lead to bad sectors over time. Make sure your drive is well-ventilated and kept in a cool environment. Avoid placing drives in enclosed spaces like closets and ensure plenty of airflow around the drive. You can also look into active cooling options like external fans.
Ensure proper airflow – Good airflow around the drive is key to preventing overheating. Don’t block vents on the drive enclosure and allow space between drives in arrays or racks for airflow. Clean out dust buildup on a regular basis.
Use surge protectors – Power surges and outages can potentially damage drive components leading to bad sectors. Always connect drives to a surge protector to regulate voltage.
Upgrade old drives – Older drives are more prone to developing bad sectors. If you have a drive over 3-5 years old, consider replacing it with a new drive to avoid potential bad sector issues. Back up data and swap out the old drive.
Regularly formatting drives can also help prevent bad sectors by re-mapping damaged areas before they fail. But remember to always backup data first before formatting.
Alternatives to Repairing Bad Sectors
Instead of trying to repair the bad sectors on a hard disk drive (HDD), there are some alternatives worth considering:
An SSD has no bad sectors to begin with. Unlike a traditional HDD that uses magnetic platters, a solid state drive (SSD) stores data in flash memory chips. This makes them immune to bad sectors caused by physical damage to a magnetic platter.
Switching to an external USB hard drive can be easier than trying to fix the bad sectors on an internal drive. Since external drives are designed to be portable and plugged/unplugged frequently, they are easy to swap out for a new one when they start to fail. Just move your data to a new external drive.
For ultimate reliability, consider abandoning local hard drives altogether and switching to cloud-based storage instead. Services like Dropbox, Google Drive, Microsoft OneDrive and others provide abundant storage that is accessible from anywhere and is far less prone to bad sectors. The cloud providers handle drive failures behind the scenes.
Citations:
When to replace a drive
There is no set threshold for the number of bad sectors that indicates a hard drive should be replaced. However, there are some general guidelines on when a drive with bad sectors should be taken out of service:
- The number of bad sectors exceeds the drive’s spare sector pool. Drives contain spare sectors that can remap bad sectors, but once this pool is exhausted the drive will have trouble remapping new bad sectors.
- The drive frequently encounters unremappable bad sectors. If the drive keeps trying to remap to a new sector but is unable to, this indicates component failure.
- The drive causes frequent crashes, failed boots, or other serious errors. Persistent serious issues likely mean replacement is needed.
- Performance has slowed to unacceptable levels. As the number of bad sectors grows, the drive has to work harder to read/write data, slowing everything down.
So in summary, even a small number of bad sectors is a red flag. If bad sectors continue to spread, the drive has trouble remapping them, or performance suffers, replacement is recommended. Critical drives should be replaced proactively once issues appear rather than waiting for total failure.
Summary
In summary, bad sectors are areas on a hard disk drive that can no longer reliably store data due to physical damage or corruption. Using a drive with bad sectors puts your data at risk and can lead to potential data loss if the bad areas spread. While software can attempt to repair bad sectors, this is not a permanent fix, and the bad areas will likely reappear over time.
Once a drive starts developing bad sectors, it’s best to replace it. Attempting to squeeze more life out of a failing drive by fixing bad sectors is not recommended, as you may lose important data. However, if the drive contains non-critical data, you may be able to continue using it temporarily. Be sure to frequently backup your data and watch for increasing numbers of reallocated sectors.
When a hard drive starts to fail, replacement is the safest option to avoid catastrophic data loss. Repairing bad sectors is risky and should only be attempted with expendable data. Ensure you have reliable backups before trying to fix drive errors.