Re: [Xen-users] 2 instances of a DomU on the same LV

[matthew pideil <matthew.pideil@xxxxxxxxxxxxxxxx>]

Le -10/01/-28163 20:59, Fajar A. Nugraha a écrit :
> On Wed, Mar 24, 2010 at 4:23 PM, Guy Roussin
> <guy.roussin@xxxxxxxxxxxxxxxx>  wrote:
>    
> > > First the basics: xen does a basic sanity check to prevent more than a
> > > domU uses the same block device/file when it's set as writable, unless
> > > user specifically overides it. The check is only on the same dom0.
> > > Nothing is done to prevent the same device used on another dom0. You
> > > need some other kind of external mechanism to prevent that.
> > >        
>    
> > Thank you Fajar, now i understand the logic.
> > Is there some "external mechanism" i can use ?
> >      
> No ready-to-use script/application that I know of.
>
>    
> > Otherwise I could develop my own simple mechanisms (shell scripts),
> >      
> You could extend /etc/xen/scripts/block. Look for check_sharing(), and
> add a custom function there to check whether a remote node/guest is
> using it.
>
> A simple way would be to set up ssh authorized_keys on both nodes and
> changing the basic commands (cat /proc/mounts, xenstore-list/read) to
> have "ssh other-host-ip" in front of it. I'm not sure how this method
> will interact with live migration though.
>
>    
> > and stop using virt-manager.
> >      
> If done correctly, you can still use virt-manager.
>
>    
Hello,

Sorry for bring back this thread but, like Fajar said, i extended the 
"/etc/xen/scripts/block" script.
Now, on the add of a new device, we check that this device is an LV and 
if it is not already opened on another
node of our non-clustered dom0s which access to the shared VG.

Problem is that this script is called by udevd when a device is added or 
removed, but in the case of migration,
this will not works.

# cat /etc/udev/xen-backend.rules | grep block
SUBSYSTEM=="xen-backend", KERNEL=="vbd*", RUN+="/etc/xen/scripts/block 
$env{ACTION}"

So how does the node could know that the device is 'mounted' by xen for 
a migration, and how
udev could handle this and does the appropriate call to the block script ?


Best regards,

--
Matthew

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