Re: [linux-lvm] Data corruption on large, multi-device filesystem

[joe@eiler.net]

I have recently run into this problem also.  I have seen it happen on SuSe 9.2,
Fedora Core 2 and 3, and vanilla kernels 2.6.8.1, 2.6.9, and 2.6.10.
All of my tests were using xfs.

It happens whenever 2 or more devices are striped together with a total volume
size greater than 2TB.  I have played with a single 4TB raid (12x 400GB RAID5)
and did not see any corruption (but I did not fill the disk either).

I initially saw the problem running video files over samba. But have recreated
the problem by simply copying some large (5GB+) files and then checking
md5sums.

I don't see any corruption on the files unless I specify the -i option to
lvcreate.  I usually see data corruption within an hour using my current tests.

Let me know if I can be of any assistance.
Joe


Quoting Jens Beyer <jbe@webde-ag.de>:

>
> Hi,
>
> I get severe data corruption using an logical volume larger
> then 2 TB. Finally I was able to track down device mappper or
> lvm as last suspects.
>
> My first guess where problems with filesystems but recently
> I tried using md / RAID0 - and didnt have any errors of any
> kind. I would prefer using LVM since we want to use snapshots
> to simplify backup, but I have no clue how to further debug.
>
> On a system with 3 devices each larger then 1 TB and a logical
> volume striped over all devices some data gets corrupted while
> written (or read ?) from disk. This shows up as md5 or crc sums
> changes on sequenced reads of files if filecache is not involved
> (by reading a lot data).
> On ext2fs there are error while writing data (kernel: EXT2-fs error
> (device dm-0): ext2_new_block: Allocating block in system zone -
>  block = 722239884), on other filesystems successive fsck/repairs
> shows corrupted metadata.
>
> The system setup is
> - Three 29160B Adaptec scsi-controller each with one
>   ATA-Disk Raid sized 1240 GB, (dual PIII, HP DL360 G2, 2 GB Ram)
> - Volume group over all three devices, logical volume stripped
>   full size (3.7 TB)
> - Filesystem either ext2fs/ext3fs (1.34), reiserfs (3.6.13) or
>   xfs (2.6.25)
>
> - host:~ # lvm version
>   LVM version:     2.00.33 (2005-01-07)
>   Library version: 1.00.21-ioctl (2005-01-07)
>   Driver version:  4.3.0
> - 2.6.10 vanilla + 2.6.10-udm1 patches
>
> The problems where initially discovered on 2.6.8, tracked on 2.6.9-udm
> and also occurs if only 2 devices (sum 2.4 TB) are used.
>
> For a limited time I will be able to further debug the system though
> it takes some time to generate more then 2 TB of data
> (max seq read/write rate is ~80 MB/s).
>
> Jens
>
> --
> Nur tote Fische schwimmen mit dem Strom
>
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