Does a Hard Drive Remember Bad Sectors After Formatting?


If you start encountering bad sectors on your hard drive and decide to format it, will it “remember” those bad sectors afterward or not? Today’s SuperUser Q&A post helps answer a curious reader’s question about bad sectors and formatting.

Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.

Photo courtesy of Scott Schiller (Flickr).

The Question

SuperUser reader chris wants to know if a hard drive remembers bad sectors after formatting:

On an NTFS-formatted hard drive with some bad sectors, does the hard drive still remember those bad sectors after Windows diskpart clean is used to remove the NTFS volume? What if clean all is used?

Does a hard drive remember bad sectors after formatting?

The Answer

SuperUser contributors Ben N and harsh have the answer for us. First up, Ben N:

NTFS remembers bad clusters. A cluster is considered bad if any sector in it is not accessible. Since the bad cluster information is stored in a specific file ($BadClus), that information will be destroyed if the NTFS volume is removed. clean and clean all are essentially the same in that regard. clean all does a more thorough job of destroying the disk’s data while clean just wipes the partition table.

Further Reading: NTFS System (Metadata) Files

The hard drive is what remembers bad sectors. Exactly how it does that depends on the model, but most modern hard drives automatically detect and remap dead sectors so that the operating system does not even know there is a problem. In that case, nothing the operating system does can affect the disk’s internal bookkeeping.

Followed by the answer from harsh:

If the operating system is encountering bad sectors, then the hard drive’s internal bad block table is probably full (as Ben N pointed out) and it is time to retire the hard drive. Hard drives typically do not stop failing.

Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.

Akemi Iwaya is a devoted Mozilla Firefox user who enjoys working with multiple browsers and occasionally dabbling with Linux. She also loves reading fantasy and sci-fi stories as well as playing "old school" role-playing games. You can visit her on Twitter and .