corrupted btrfs disk image file recovery | Arch Linux Community | Page 1

full flame Jun 19, 2024, 3:29 PM

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had a catastrophic failure of a writethrough disk cache containing btrfs vm disk images. both completely unmountable. i've tried the usual recovery approaches to no avail. offering reward for successful data recovery. file carving works to a minimal extent but is useless without path data.

regular mount attempt:

[10113.417241] BTRFS info (device loop0): first mount of filesystem 109fc8c0-557f-4ea1-9de8-ac8888464f6d
[10113.417276] BTRFS info (device loop0): using crc32c (crc32c-intel) checksum algorithm
[10113.417290] BTRFS info (device loop0): disk space caching is enabled
[10113.439147] BTRFS error (device loop0): level verify failed on logical 75317248 mirror 1 wanted 1 found 0
[10113.445609] BTRFS error (device loop0): level verify failed on logical 75317248 mirror 2 wanted 1 found 0
[10113.445697] BTRFS warning (device loop0): couldn't read tree root
[10113.447289] BTRFS error (device loop0): open_ctree failed

attached screenshot is dmesg from when the failure occurred

rancid niche Jun 19, 2024, 3:32 PM

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@full flame you said there was money involved?

full flame Jun 19, 2024, 3:33 PM

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rancid niche <@97090889423261696> you said there was money involved?

if you succeed, sure

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beware that i've tried all the usual recovery steps you'd find with brief google searches

rancid niche Jun 19, 2024, 3:33 PM

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this is in a vm?

full flame Jun 19, 2024, 3:33 PM

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and the people in #btrfs on irc have told me "... good luck"

full flame Jun 19, 2024, 3:34 PM

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rancid niche this is in a vm?

these are raw disk images of a btrfs partition that were used as vm drives

rancid niche Jun 19, 2024, 3:34 PM

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did you make backups ie with snapper?

full flame Jun 19, 2024, 3:34 PM

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compress=zstd

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if i had backups i wouldn't be looking to pay people to recover the data

grizzled mason Jun 19, 2024, 3:34 PM

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I think killer means snapshots, not backups

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snapshots that might also be corrupted

rancid niche Jun 19, 2024, 3:35 PM

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this

full flame Jun 19, 2024, 3:35 PM

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doubt it. either way the btrfs tools don't dare even attempt to read the disks much so

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grizzled mason Jun 19, 2024, 3:36 PM

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and you know, covering basics, I assume that you can't mount the drive in another system because that fails?

full flame Jun 19, 2024, 3:37 PM

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i'm already on another system, i have dd copies of the drives at failure-time stored on there, and that's what i am operating on right now

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mounting the images presents the same problems as attempting to mount them in the original system yes

grizzled mason Jun 19, 2024, 3:37 PM

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yeah, sorry for stupid question, I just like to make sure other methods don't randomly work even if they shouldn't

full flame Jun 19, 2024, 3:38 PM

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this is >1tb of data, so no matter how many recent writes have been corrupted before the vm failed, surely the vast majority of it should be intact since it was at rest

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(across two btrfs partitions)

grizzled mason Jun 19, 2024, 3:46 PM

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@chilly imp do you know / know anyone?

graceful flint Jun 19, 2024, 6:33 PM

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full flame had a catastrophic failure of a writethrough disk cache containing btrfs vm disk...

try btrfs restore
it will attempt to read the filesystem without mounting and copy files
you can choose what file with an argument controlling patterns and another controlling subvils

grizzled mason Jun 19, 2024, 6:34 PM

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graceful flint try btrfs restore it will attempt to read the filesystem without mounting and c...

Just to let you know that’s been tried and failed

graceful flint Jun 19, 2024, 6:35 PM

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i haven't seen it mentioned explicitly, just wanna make sure