Why doesn't use checksum method?
Posted: 17 Apr 2023, 15:09
There are several methods:
1. Absolutely reliable: comparing each byte (slow).
2. Almost as reliable: checksum - MD5, SHA, etc. (relatively fast).
3. Everything else (very unreliable): comparing sizes, creation or modification dates, attributes.
I was surprised to discover that the program relies entirely on unreliable methods.
I tried this program (incremental, 7-ZIP LZMA) and found that it couldn't handle my task. I needed to make a backup of a folder with a game (6 GB) and an installed mod (700 MB). Periodically, the launcher of this mod downloads an archive containing the entire mod and unpacks it into the game folder. All other backup programs I tested (about 5) easily completed the task and created an archive of size 10 MB after updating the mod, but Reflector created an archive of size 700 MB. This means that when updating the mod, also restored the archive attribute and Reflector was easily fooled.
1. Absolutely reliable: comparing each byte (slow).
2. Almost as reliable: checksum - MD5, SHA, etc. (relatively fast).
3. Everything else (very unreliable): comparing sizes, creation or modification dates, attributes.
I was surprised to discover that the program relies entirely on unreliable methods.
I tried this program (incremental, 7-ZIP LZMA) and found that it couldn't handle my task. I needed to make a backup of a folder with a game (6 GB) and an installed mod (700 MB). Periodically, the launcher of this mod downloads an archive containing the entire mod and unpacks it into the game folder. All other backup programs I tested (about 5) easily completed the task and created an archive of size 10 MB after updating the mod, but Reflector created an archive of size 700 MB. This means that when updating the mod, also restored the archive attribute and Reflector was easily fooled.