Why doesn't use checksum method?

Questions about Cobian Reflector
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RandomName
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Joined: 17 Apr 2023, 13:46

Why doesn't use checksum method?

Post by RandomName »

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.
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cobian
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Re: Why doesn't use checksum method?

Post by cobian »

Those methods need at least one backup to exist for comparation. The archive attribute (the classical method) doesn't.
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Luis Cobian
Cobian Backup's creator
RandomName
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Joined: 17 Apr 2023, 13:46

Re: Why doesn't use checksum method?

Post by RandomName »

Do you plan to add this method to your program? Without its availability, using the Reflector is too risky.
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cobian
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Re: Why doesn't use checksum method?

Post by cobian »

Perhaps.
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Luis Cobian
Cobian Backup's creator
halfmann
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Joined: 17 Mar 2022, 12:53

Re: Why doesn't use checksum method?

Post by halfmann »

Yes, please!!!
jameshand
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Joined: 29 May 2023, 06:11

Re: Why doesn't use checksum method?

Post by jameshand »

Your methods sound amazing
noahharold
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Joined: 28 Oct 2024, 03:15

Re: Why doesn't use checksum method?

Post by noahharold »

It sounds like you're facing a frustrating issue with Reflector's backup method. Relying solely on unreliable methods can definitely lead to inefficiencies, especially with large files. It's surprising that it didn't utilize checksums for verification. Have you considered reaching out to their support for clarification on this?
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cobian
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Re: Why doesn't use checksum method?

Post by cobian »

It can use crc verification (unchecked by default)
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Luis Cobian
Cobian Backup's creator
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