[DRBD-user] block-drbd and Xen

Alexandre Biancalana biancalana at gmail.com
Tue Sep 2 13:45:48 CEST 2008

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


On 9/2/08, Jerry Amundson <jamundso at gmail.com> wrote:
> On Mon, Sep 1, 2008 at 10:08 PM, Alexandre Biancalana
>
> <biancalana at gmail.com> wrote:
>  > On 9/1/08, Jerry Amundson <jamundso at gmail.com> wrote:
>  >> On Mon, Sep 1, 2008 at 8:25 PM, Alexandre Biancalana
>  >>  <biancalana at gmail.com> wrote:
>  >>  > Hi list,
>  >>  >
>  >>  >  I know that this subject was discussed before but I don't find any
>  >>  > definitive answer to this question, so I hope that this message can
>  >>  > help people finding this in future.
>  >>
>  >>
>  >> Doesn't matter. Most people seem to find the *official* answer, which
>  >>  *official* people refuse to change, yet many times just does not work.
>  >
>  > Hi Jerry !
>  >
>  > I just want something that work....
>
>
> Naturally.
>
>
>  >>  >  I installed Debian 4 (etch), Xen 3.2 and DRBD 8.0.13 (from
>  >>  > backports).  The objective is to build a two-node Linux HA to
>  >>  > virtualize some legacy services and development machines.
>  >>  >
>  >>  >  My question is about block-drbd script, when I try to boot a virtual
>  >>  > machine using a drbd disk resource like this:
>  >>  >
>  >>  > disk   = [ 'drbd:app01,hda,w' ]
>  >>
>  >>
>  >> Why did you use that?
>  >
>  > Because theoretically when I use drbd: instead phy: Xen call
>  > block-drbd script that  handles the necessary DRBD resource state
>  > transitions, right ?
>
>
> What I meant to ask is, where, specifically, you obtained the idea,
>  instead of the more "xen-oriented" phy: syntax ...

The both url tell to use this way

http://www.drbd.org/users-guide-emb/s-xen-configure-domu.html
http://fghaas.wordpress.com/2007/09/03/drbd-806-brings-full-live-migration-for-xen-on-drbd/

>
>
>  >> Of course phy: works great. Fortunately, with allow-two-primaries;,
>  >>  and other controls, DRBD 8.x can do Xen live migration, even using
>  >>  phys: ...
>  >
>  > I already read that, but if everything (including state transition and
>  > consequently live migration) work directly with phy: why block-drbd
>  > (drbd:) exists at all ???
>
>
> Because, when it works, it's more "modular", and can blend in with the
>  transparency that comes with virtualization. For now, however, it just
>  wastes time for those of us who choose to call attention to it... ;-)

So is something missing in the script or in Xen ? If this does not
work why the documentation points to that ?

On DRBD point's of view, what is the safe and correct method to use
Xen live migration with DRBD resources without run into any race or
danger of corrupt the data ?

I need to be sure what's the right method before deploy this in a
production environment.

Thank you for your time

Alexandre



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