Re: [Xen-users] Raid 5+0 Problems Under Xen

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Sun, Feb 21, 2010 at 05:48:47AM -0500, chris wrote:
> I am experiencing a weird issue with a raid 5+0 under dom0. I am
> running xen 3.2 from debian lenny which has the 2.6.26-2-xen-amd64
> dom0 kernel. There are 6 1TB sata disks which are arranged in 2 sets
> of 3 disk raid5's which are raid0'd together. Chunk size on all arrays
> is 64k and I was able to create and sync all arrays with no issues,
> then initialized lvm on the raid0 and created 2 lv's all with no
> issues. I was able to install 2 guests with no apparent problems
> however after 2 days I noticed errors in the guests that their disks
> had bad blocks. I checked dom0 and noticed lots of messages like
> these:
> 
> [305012.467758] raid0_make_request bug: can't convert block across
> chunks or bigger than 64k 2385277 4
> 
> I have posted this to linux-raid mailinglist where they have indicated
> that this bug is likely due to xenified kernel.
> 
> A quote from the linux-raid mailinglist:
> 
> > This looks like a bug in 'dm' or more likely xen.
> > Assuming you are using a recent kernel (you didn't say), raid0 is
> > receiving a request that does not fit entirely in on chunk, and
> > which has more than on page in the bi_iovec.
> > i.e. bi_vcnt != 1 or bi_idx != 0.
> >
> > As raid0 has a merge_bvec_fn, dm should not be sending bios with more than 1
> > page without first cheking that the merge_bvec_fn accepts the extra page.
> > But the raid0 merge_bvec_fn will reject any bio which does not fit in
> > a chunk.
> >
> > dm-linear appears to honour the merge_bvec_fn of the underlying device
> > in the implementation of its own merge_bvec_fn.  So presumably the xen 
> > client
> > is not making the appropriate merge_bvec_fn call.
> > I am not very familiar with xen:  how exactly are you making the logical
> > volume available to xen?
> > Also, what kernel are you running?
> >
> > NeilBrown
> 
> Unfortunately since I am running 3.2 from what I understand there are
> limited dom0 options, so I am not sure if there is any advice on this
> mailinglist or if I should bring this up on xen-devel. I have detailed
> raid information and errors at http://pastebin.com/f6a52db74
> 
> I would appreciate any advice or input on this issue.
> 

Try with different dom0 kernel:
http://wiki.xensource.com/xenwiki/XenDom0Kernels

I'd suggest linux-2.6.18-xen or some forward-port of it (2.6.31).

If different dom0 kernel doesn't help, then try emailing to xen-devel with the 
info/quote above included.

-- Pasi


_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users