Linux-BTRFS Archive on lore.kernel.org
 help / color / Atom feed
From: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
To: Richard Weinberger <richard@nod.at>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: Decoding "unable to fixup (regular)" errors
Date: Fri, 8 Nov 2019 17:25:57 -0500
Message-ID: <20191108222557.GT22121@hungrycats.org> (raw)
In-Reply-To: <1374130535.78772.1573251716407.JavaMail.zimbra@nod.at>

[-- Attachment #1: Type: text/plain, Size: 3068 bytes --]

On Fri, Nov 08, 2019 at 11:21:56PM +0100, Richard Weinberger wrote:
> ----- 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

Even the disks?  We see RAM failures in disk drive embedded boards from
time to time.

> >> 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.
> 
> Thanks,
> //richard

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 195 bytes --]

  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
2019-11-08 22:25     ` Zygo Blaxell [this message]
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

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191108222557.GT22121@hungrycats.org \
    --to=ce3g8jdj@umail.furryterror.org \
    --cc=linux-btrfs@vger.kernel.org \
    --cc=richard@nod.at \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-BTRFS Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-btrfs/0 linux-btrfs/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-btrfs linux-btrfs/ https://lore.kernel.org/linux-btrfs \
		linux-btrfs@vger.kernel.org
	public-inbox-index linux-btrfs

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-btrfs


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git