----- 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.
Thanks,
//richard
