This option allows you to check the health of photo archive.
A hash sum is a number that can be used to uniquely identify a file and its contents. A hash sum can be thought of as a 'fingerprint' of a file. MD5 hash sum is very sensitive to the changes and can register changes of one bit in very large file. And therefore, the hash files allow to determine were whether changes in your photos. To generate (or test) a hash file requires additional time. The rate of generation (or testing) is at about 30MB / sec. Spending a little time, you will reach the full safety of your archive. You can check hash sum at all restore and sync operations. We write hash sum in a separate text file with md5 extension. The name of hash file matches the name of the image file. If the file is damaged or altered it will never be placed in the archive. This avoids duplication of errors which then fall into the archive and backup at the same time. The corresponding entry appears in the log file. This will be a signal to replace or restore a corrupted file.
To facilitate the search the error information into a log file, you can set the logging level.
We encourage you to periodically check the backups, with intervals of at least 2 times a year, especially if copies are on CD or DVD disks.