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#1 2019-11-12 00:44:08
- Fractale
- Member
- Registered: 2016-03-11
- Posts: 6
How to image a failling sd card witch return different read value?
when I try to copy some files from this sd card I always get a different version of the files (usually one byte is different).
Is there any way to create disk images (with dd for example) and then "average the diff" to get what's actually in the sd card?
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#2 2019-11-12 02:02:59
- xse
- Member
- Registered: 2019-01-08
- Posts: 36
Re: How to image a failling sd card witch return different read value?
Hi,
Is there any way to create disk images (with dd for example) and then "average the diff" to get what's actually in the sd card?
Data recovery is a huge topic and depending on the type of files you want to recover, a "one byte difference" might not cause any issues.
I'm not aware of a tool that does exactly what you are describing but it does not sound that hard to make.
have a look at ddrescue which might be able to detect read errors and retry when needed, it's a long process but i've used it successfully.
Carefully explaining your problem is half the solution.
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#3 2019-11-12 03:06:05
- Fractale
- Member
- Registered: 2016-03-11
- Posts: 6
Re: How to image a failling sd card witch return different read value?
Data recovery is a huge topic and depending on the type of files you want to recover, a "one byte difference" might not cause any issues.
it's photos. so I imagine some photos will be corrupted
I'm not aware of a tool that does exactly what you are describing but it does not sound that hard to make.
have a look at ddrescue which might be able to detect read errors and retry when needed, it's a long process but i've used it successfully.
ddrescue give me different output everytime. some location are read differently every time I try.
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#4 2019-11-12 08:55:33
- seth
- Member
- Registered: 2012-09-03
- Posts: 51,213
Re: How to image a failling sd card witch return different read value?
Use another card reader/cable.
It's rather unlikely that exactly one byte per file is corrupted and causing random reads. The cards usually fail to write cells and later on maybe reading altogether. As long as a NAND cell can be read, the data in it is very stable.
Thus it's more likely the bytes acre corrupted on the way from the card to your disk, maybe even on the disk (try reading them into tempfs - or, better, a completely different system incl. different RAM)
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