Re: Ceph + Xen - RBD io hang

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John,

I've never installed anything on Scientific Linux. Are you sure that
QEMU has RBD support?

I have some wip-doc text, which I'm going to move around shortly. You
can see the yum install requirements here:

http://ceph.com/docs/wip-doc-install/install/yum-priorities/
http://ceph.com/docs/wip-doc-install/install/install-qemu/#rpm-packages

Make sure you can run QEMU commands on RBD first, since that's a dependency.

http://ceph.com/docs/wip-doc-install/rbd/qemu-rbd/

On Mon, Oct 28, 2013 at 12:01 PM, John Morris <john@xxxxxxxxxxx> wrote:
> I'm encountering a problem with RBD-backed Xen.  During a VM boot,
> pygrub attaches the VM's root VDI to dom0.  This hangs with these
> messages in the debug log:
>
> Oct 27 21:19:59 xen27 kernel:
>   vbd vbd-51728: 16 Device in use; refusing to close
> Oct 27 21:19:59 xen27 xenopsd-xenlight:
>   [xenops] waiting for backend to close
> Oct 27 21:19:59 xen27 kernel:
>   qemu-system-i38[2899]: segfault at 7fac042e4000 ip 00007fac0447b129
>   sp 00007fffe7028630 error 4 in qemu-system-i386[7fac042ed000+309000]
>
> More details here:
>
> http://pastebin.ca/2472234
>
>   - Scientific Linux 6
>   - 64-bit, Phenom CPU
>   - Ceph from RPM ceph-0.67.4-0.el6.x86_64
>   - XenAPI from Dave Scott's technology preview
>   - two btrfs-backed OSDs with journals on separate drives
>   - various kernels, incl. 3.4.6 from Dave Scott's repo and 3.11.6
>     from elrepo.org.
>
> This thread (whose Subject: I borrowed) describes what I'm seeing quite
> well, but no resolution was posted:
>
> http://comments.gmane.org/gmane.comp.file-systems.ceph.user/3636
>
> In my case, udevd starts a 'blkid' process that holds /dev/xvdb open.
> Like in James's case, any interaction with the device will hang, and
> usually can't be killed.  This same problem prevents the machine from
> completing shutdown.
>
> In that thread, Sylvain Munaut says the OSD and kernel driver shouldn't
> be run in the same host.  I believe my setup does not violate that,
> since the rbd kernel module is not loaded, and instead the device is
> attached through the xen_blkfront module instead.
>
> Thanks-
>
>         John
> _______________________________________________
> ceph-users mailing list
> ceph-users@xxxxxxxxxxxxxx
> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com



-- 
John Wilkins
Senior Technical Writer
Intank
john.wilkins@xxxxxxxxxxx
(415) 425-9599
http://inktank.com
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