You need to be sure you know *why* it happened. What is the partition layout of your Amiga? What filesystem (FFS? PFS? SFS?) are you using? What version of Kickstart and Workbench are you running? What did you do just before it happened?
You need to think about these questions to ensure it doesn't happen again. For example, certain partition layouts are invalid on OS3.1 and below and can cause validation/checksum problems, and rebooting while something is being written to the disk can cause this problem, particularly if you are using FFS.
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moto