Q: I only have a single hard disk that is used to boot my OS, how can I test it?

Write + Verify: The program will write a test pattern to the disk and verify the pattern was written successfully.

Read + Write + Verify + Restore: The program will write a test pattern to the disk, verify the pattern was written successfully, and then restore the original data.

Read + Wipe Damaged + Read: Will scan the entire hard drive surface to find bad sectors, if bad sectors are found, they will be overwritten, and read again to make sure they were written successfully this time.

Read: Will scan the entire hard drive surface to find bad sectors.

Q: What's the difference between the tests? If something seems to be wrong with the drive, it's better to back up the data and use the 'Write + Verify' test, which will erase all of the data on the disk. If you're recovering from a power failure, then 'Read + Wipe Damaged + Read' is the fastest way to wipe out the bad sectors and avoid any issue with software that does not respond well to bad sectors. This is my hard drive after wiping out a bad sector that was created during a power failure: Well, the data stored on the sector is invalid, but if your hard drive is functioning properly, you can overwrite the bad sector (and now it won't be 'bad' anymore since the sector checksum will be updated as well).

Power failure during write is one common reason, hard drive malfunction is another common reason. When a sector is read from your hard drive, it's expected that the sector checksum will match the sector data, if that is not a case, the hard disk knows something went wrong during the write operation, that's called a bad sector. Hard drives write data in block units (sectors), every time a hard drive update a sector, it also updates a checksum (stored immediately after the sector data). This simple utility was designed to help you find out if your hard drive has reached its end of life.

Hard disk health checker