[DRBD-user] Fwd: Re: drbd stops sync on LVM

Lars Ellenberg lars.ellenberg at linbit.com
Wed Sep 8 17:00:45 CEST 2010

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

On Wed, Sep 08, 2010 at 04:53:12PM +0200, Eric Deschamps wrote:
> Le 08/09/2010 16:30, Lars Ellenberg a écrit :
> > 
> > See how not one of them references DRBD,
> > but all directly use the lower level LVs directly?
> > 
> > If you bybass DRBD, you cannot expect it to magically know
> > about, and sync, your changes.
> > 
> The VMs are directly on LVs and LVs are the backing devices for DRBD
> nodes, as in the user guide:
> http://www.drbd.org/users-guide-emb/s-lvm-lv-as-drbd-backing-dev.html
> The sync works (actually, makes a snapshot) if I use drbdadm
> invalidate-remote.

Ok, I'll try again.
You have:

 VM         [DRBD] -------- [DRBD] remote node
  \          /
   \        /
 [logical volume]

 (DRBD does not see or know about any changes done by VM)

You need:
            [DRBD] -------- [DRBD] remote node
 [logical volume]

 (DRBD sees every change done by the VM, and thus
  has a chance to mirror the changes over).


If you trigger a full sync in [what you have],
of course everything that is in the LV is synced over.
Though, if it is changed during that time directly from the VM,
it will be inconsistent.

: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

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