An HDD Has 800 Bad Blocks: Clone First or Run CHKDSK?
TL;DR:
Do not run CHKDSK /r on a hard drive with hundreds of bad blocks before imaging, as the intensive scan cannot fix physically unreadable sectors and will further stress the failing hardware.
● Standard file-system cloning programs fail on bad sectors, requiring the use of an error-aware, resumable tool like GNU ddrescue with a separate healthy destination and a saved mapfile.
● Any data recovery attempts or repair utilities must be executed strictly on the newly created clone rather than the original damaged source.
● Stop DIY rescue attempts immediately if the drive shows worsening mechanical symptoms, or simply replace the drive without scanning if the files are replaceable and can be downloaded again.
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With hundreds of bad blocks already reported, do not run CHKDSK /r before imaging. First decide whether the data is worth professional recovery; only then consider a controlled sector-level rescue onto other storage.
In this r/datarecovery case about 800 bad blocks, the owner had a replacement drive but asked whether to run CHKDSK or use a normal cloning program first. The files were inconvenient, but replaceable.
CHKDSK Is Not a Bad-Sector Retrieval Strategy
As Microsoft documents, CHKDSK /r checks sectors and attempts to recover readable information while also performing file-system repairs. It cannot make physically unreadable sectors readable again, and a long pass can stress a failing drive.
A file-system-aware backup or migration clone can also fail when the disk has unreadable sectors. Its successful completion does not mean deleted or orphaned content was preserved byte for byte.
Use a Resumable Rescue Image Only When the Risk Is Acceptable
For a drive that still identifies correctly, a skilled user may use an error-aware tool such as GNU ddrescue with a separate healthy destination and a saved mapfile. Work on the resulting copy rather than running repair utilities on the original.
Because this Reddit user said the data could be downloaded again, replacing the drive may be more rational than risking further reads. For irreplaceable files, stop DIY as soon as the source shows worsening mechanical or connectivity symptoms.