Recommendations for Volume Rebuild

Before rebuilding the disk directory with Volume Rebuild, take a look at the Technical Comparison window that opens before the changes are made.  If the number of files and folders and the total amount of disk space occupied by the files on the original volume and the proposed rebuild match, it should be safe to replace the disk directory. If the numbers do not match, and the difference is reported in red, it is best not to proceed with the rebuild.  Green replacement numbers reflect an improvement in the directory structures, and the rebuild can proceed.

In general, be sure to have a backup of any files you cannot replace before you replace a disk directory.  Failures are extremely rare, but that will be of little consolation if you experience one but have no backup.