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From: Richard Weinberger <>
To: Zygo Blaxell <>
Subject: Re: Decoding "unable to fixup (regular)" errors
Date: Fri, 8 Nov 2019 23:21:56 +0100 (CET)
Message-ID: <> (raw)
In-Reply-To: <>

----- Ursprüngliche Mail -----
> btrfs found corrupted data on md1.  You appear to be using btrfs
> -dsingle on a single mdadm raid1 device, so no recovery is possible
> ("unable to fixup").
>> The system has ECC memory with md1 being a RAID1 which passes all health checks.
> mdadm doesn't have any way to repair data corruption--it can find
> differences, but it cannot identify which version of the data is correct.
> If one of your drives is corrupting data without reporting IO errors,
> mdadm will simply copy the corruption to the other drive.  If one
> drive is failing by intermittently injecting corrupted bits into reads
> (e.g. because of a failure in the RAM on the drive control board),
> this behavior may not show up in mdadm health checks.

Well, this is not cheap hardware...
Possible, but not very likely IMHO

>> I tried to find the inodes behind the erroneous addresses without success.
>> e.g.
>> $ btrfs inspect-internal logical-resolve -v -P 593483341824 /
>> ioctl ret=0, total_size=4096, bytes_left=4080, bytes_missing=0, cnt=0, missed=0
>> $ echo $?
>> 1
> That usually means the file is deleted, or the specific blocks referenced
> have been overwritten (i.e. there are no references to the given block in
> any existing file, but a reference to the extent containing the block
> still exists).  Although it's not possible to reach those blocks by
> reading a file, a scrub or balance will still hit the corrupted blocks.
> You can try adding or subtracting multiples of 4096 to the block number
> to see if you get a hint about which inodes reference this extent.
> The first block found in either direction should be a reference to the
> same extent, though there's no easy way (other than dumping the extent
> tree with 'btrfs ins dump-tree -t 2' and searching for the extent record
> containing the block number) to figure out which.  Extents can be up to
> 128MB long, i.e. 32768 blocks.

Thanks for the hint!

> Or modify 'btrfs ins log' to use LOGICAL_INO_V2 and the IGNORE_OFFSETS
> flag.
>> My kernel is 4.12.14-lp150.12.64-default (OpenSUSE 15.0), so not super recent
>> but AFAICT btrfs should be sane
>> there. :-)
> I don't know of specific problems with csums in 4.12, but I'd upgrade that
> for a dozen other reasons anyway.  One of those is that LOGICAL_INO_V2
> was merged in 4.15.
>> What could cause the errors and how to dig further?
> Probably a silent data corruption on one of the underlying disks.
> If you convert this mdadm raid1 to btrfs raid1, btrfs will tell you
> which disk the errors are coming from while also correcting them.

Hmm, I don't really buy this reasoning. Like I said, this is not
cheap/consumer hardware.


  reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-05 22:03 Richard Weinberger
2019-11-08 22:06 ` Richard Weinberger
2019-11-08 22:16   ` Zygo Blaxell
2019-11-08 22:09 ` Zygo Blaxell
2019-11-08 22:21   ` Richard Weinberger [this message]
2019-11-08 22:25     ` Zygo Blaxell
2019-11-08 22:31       ` Richard Weinberger
2019-11-08 23:39         ` Zygo Blaxell
2019-11-09  9:58           ` checksum errors in orphaned blocks on multiple systems (Was: Re: Decoding "unable to fixup (regular)" errors) Richard Weinberger
2019-11-13  3:34             ` Zygo Blaxell
2019-11-09 10:00           ` Decoding "unable to fixup (regular)" errors Richard Weinberger
2019-11-13  3:31             ` Zygo Blaxell
2019-11-13 18:17             ` Chris Murphy
2019-11-13 18:24               ` Chris Murphy
2019-11-16  6:16               ` Zygo Blaxell

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