Bad sector

When a bad sector is found and marked, the operating system like Windows or Linux will skip it in the future.

In case of power loss, bit rot (more likely on floppy disks), or firmware issues, the on-disk format can be corrupt beyond what the error correcting code can fix.

[1] On the other hand, sectors broken physically cannot be restored: writing would fail, forcing a remap.

Larger patches occur throughout use, due to head crash, wear-and-tear, physical shock, or dust intrusion.

In the normal operation of a hard drive, the detection and remapping of bad sectors should take place in a manner transparent to the rest of the system and in advance before data is lost.

For instance, to make sector 10 bad: hdparm has a --make-bad-sector command that works similarly.

Errors recovered by ECC, which are reported by enterprise drives (using the SCSI command set), also suggest a higher chance of a bad sector in the future.