Also if an extra report or LUT file is written without being used in this hash, then the check fails without giving any information as to what caused the failure.Īlso human comparison of hashes for multiple sets of files is not verification. So even with all the correct files, combining the hashes in a different order will result in a different result. Is the sorting alphabetically over the whole tape, or are the folders sorted first, then the contents? What sort type is used, pure alphanumeric or a numeric text-based?Īre extra files like reports included? What about sidecar files like LUTs, are they excluded from this master hash? The reason for this is that when making a hash from individual hashes the order of the files needs to be specified. YoYotta doesn't create a single hash as we think it is of little value and can easily give false negatives. Single hash or checksum for entire tapes or drives After verification is complete the checksums can also be stored in MHL, MD5, CSV, ALE and PDF files locally and also on each copy. YoYotta does this automatically at high speed whenever a file is restored. This means that the file can be easily re-checked at any time in the future. The checksums are stored as extended attributes for every copied file. If there are any issues then a warning is logged. If the two checksums do not match then YoYotta rereads the destination file and generates MD5 and xxHash checksums and compares these against the source checksums. So YoYotta archives will always be compatible with any delivery specification.ĭuring verification YoYotta reads back every file from the destination, generates an xxHash checksum and compares this against the source checksum. Whilst copying each file YoYotta generates both MD5 and xxHash checksums, even when Quick Verify is enabled. YoYotta does not support these and we would not recommend using them to avoid confusion and incompatibilities.Ĭhanges to the contents of the file give a different checksum, so verifying by comparing checksums is a great way to ensure that a file has not been changed and is an exact copy of the original. There are other xxHash variants XXH3 and XXH128. This is the industry standard xxHash and is compatible with other workflow software. XxHash is a newer checksum that is faster to generate, YoYotta uses the xxHash64be which is a 64bit big endian algorithm. As shown here an MD5 checksum can also be generated using the terminal. The calculation of an MD5 is an industry standard so the integrity can be checked on any system. An MD5 checksum is a 32 digit hexadecimal number that represents the hash of the contents of a file.
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