Re: csum errors in VirtualBox VDI files

[Henk Slager <eye1tm@gmail.com>]

On Tue, Mar 22, 2016 at 9:03 AM, Kai Krakow <hurikhan77@gmail.com> wrote:
> Hello!
>
> Since one of the last kernel updates (I don't know which exactly), I'm
> experiencing csum errors within VDI files when running VirtualBox. A
> side effect of this is, as soon as dmesg shows these errors, commands
> like "du" and "df" hang until reboot.
>
> I've now restored the file from backup but it happens over and over
> again.
>
> On another machine I'm also seeing errors with big files in the
> following scenario (apparently an older kernel, 4.1.x I afair):
>
> # ntfsclone --save /dev/md126p2 -o rescue.ntfs.img
>                    ^ big NTFS partition   ^ file on btrfs
>
> results in a write error and the file system goes read-only.
>
> Both systems have in common they are using btrfs on bcache with
> compress=lzo,autodefrag,nossd,discard (mraid=1,draid=0 and
> mraid=1,draid=single).

autodefrag,nossd:  I am using these too on bcached btrfs, so far no
issues (including kernel 4.5.0). I have been writing bigfiles (> 50G)
without problems.
compress=lzo: I have used it on bcached btrfs in the past, worked fine
discard: I am not sure what this should do on top of /dev/bcacheX ; I
don't know how this relates to the bcache discard; I currently have
bcache setting:  Discard?  False

I am not saying that the last mount option is the direct cause of the
problems you experience, it is just that I don't know its impact
currently.

> The system mentioned first is running Kernel 4.5.0 with Gentoo
> patch-set. I upgraded from the last 4.4.x kernel when I first
> experienced this problem. The first time the problem resulted in a
> duplicate extent which btrfsck wasn't able to fix, that's when I first
> restored from backup. But now I'm getting csum errors in this file over
> a over again, plus when rsync has run for backup, the system no longer
> responds to "du" and "df" commands - it just hangs.
>
> Known problem? Does it help if I send debug info? If so, please
> instruct.
>
> --
> Regards,
> Kai
>
> Replies to list-only preferred.
>
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