Mac hard disk corruption

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chridd
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Mac hard disk corruption

Postby chridd » Wed Feb 28, 2018 5:09 am UTC

About a week ago my Mac was experiencing problems and unable to start up, so I took it in to be repaired. I got it back today, but I seem to have found a problem: some of my files are corrupted. In particular, the corrupted files that I've found so far seem to be multiples of 0x10000 bytes long, and at least one of them seems to have been truncated (i.e., the data at the beginning is intact, but it ends early). Unfortunately, I used the computer a bit before a noticed the corruption/realized that I probably shouldn't be saving new files when it's like this (and also the people who worked on it upgraded the operating system). Also, my backup seems to be corrupted (see here).

Any advice for what to do? Is there a way to make a copy of the disk, including parts that the system thinks don't belong to a file? Any way to recover files?
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Tub
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Re: Mac hard disk corruption

Postby Tub » Wed Feb 28, 2018 2:01 pm UTC

Even booting from the corrupt drive will cause further writes to the drive. If that drive contains the only copies of important files, I'd avoid that.

See if you can get your time machine working before you touch the corrupt mac again.

If the time machine is lost, the first step would be to make a carbon copy to an external USB drive - if your hdd has a hardware failure, you need to get the data somewhere else. Either remove the drive and put it in a different computer (if the drive bay is accessible), or boot from a linux usb stick or something (if that's possible on a mac), then pull a full physical image that included all blocks. On mac or linux, you can just use dd; google will find you a suitable tutorial.

Once you have a backup, copy the important files one by one somewhere safe, checking if they're ok. Make a list of corrupt files. Then try any data recovery tool you can find, checking if they fixed the corrupt files, but make sure these tools write the recovered files someplace else; not overwriting the backup.

That will still take a lot of time and manual intervention to piece the data back together. You can also pay a specialist to do these things for you, if you have the money. But either way, there's no guarantee.


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