Re: [linux-lvm] Random file system errors

["Clyde E. Kunkel" <rascal.jumper-747@cox.net>]

On 04/27/2009 09:52 PM, Gaute Lund wrote:
> I have searched the web and the mailing list without finding anything
> similar to this.
>
> At home I have an LVM setup. Reading data gives random errors. I only
> recently discovered it's an LVM issue. I think.
>
> The issue: If I md5sum largeish files, or test archives, I sometimes get
> errors or randomly different md5sums. Like now, I have 11 folders, all with
> rar files in parts: some 300 15MB pieces in 6 folders/sets, totaling 4,2GB,
> and 560 50MB pieces in 5 folders/sets, totaling 23G.
>
> OK, so I "rar t" all of these 5 times over. Errors pop up randomly, 52 times
> in the 50MB pieces, 10 times in the 15MB pieces. That's about 1 error for
> every 2,1GB of data read. Md5suming multiple files gives about the same
> error rate.
>
> If I run repeated test on a rar set small enough to fit in cache mem, I get
> errors, but they are indentical with each run.
>
> Is it really an lvm problem? Well, I have created new LVs and use different
> filesystems, ext3, xfs, jfs - they're all the same. If I create an md on
> some other disks, and put a filesystem on it, without LVM, no problems.
>
> I can't find any other errors, in any logs or dmesg. The errors weren't
> there to begin with, they came at one point and got worse. It took a while
> before I realized it was a generic disk problem, and for a period I kind of
> gave up on it. So it's been there for ... maybe six months?
>
> The VG consist of two software RAID 5 md's, one consisting of four 200GB
> IDEs, one of five 500GB SATAs, yielding av VG totaling 2,37TB. Other
> hardware is 4GB memory and a Core 2 Duo 6600 CPU.
>
> Machine runs Ubuntu 8.10 with kernel 2.6.27-11, and
>    LVM version:     2.02.39 (2008-06-27)
>    Library version: 1.02.27 (2008-06-25)
>    Driver version:  4.14.0
>
> But the VG was originally created long ago, on LVM1 even.
>
> Well, I guess that's it. Any other information that could be helpful? Any
> way I could debug this?
>
> Best regards
> Gaute Lund
>    

I am seeing the same thing with large (distros on DVDs) ISO files also.  
Running md5sum or sha1sum on the file gives different results each time 
and burning the iso gives a dvd that contains files with errors.  I ran 
memory tests over night and all was good.  I turned on smartd checking 
and ran disk checks and all is ok and I continue to look for disk errors 
on a periodic basis and all is well.

The linux system is Fedora rawhide, but the problem also exists in 
Fedora 9 and 10.  The files are being downloaded with wget to a Download 
directory on my home directory which is an ext3 LV mounted on an ext4 
home filesystem.  Wgeting to a standard non-LV ext3 parition results in 
good isos which demonstrate consistent sha1sums.  If I cp the good iso 
to the LV Download directory, problems again occur.  So far the problem 
only manifests with dvd size iso files.  CD size iso files are fine.

I first noticed this problem several months ago, but have not bz'd it 
since I cannot yet for sure say it is LVM causing the problem.  However, 
I think at this point I have eliminated wget as the problem but not 
ext4.  I need to create an ext3 LV for / to test on.

Any guidance on error capturing or any testing features of LVM2 that can 
be turned on?

Thanks.