[DRBD-user] Question about Linux-HA, stonith and data loss

paddy paddy at panici.net
Fri Dec 23 16:58:27 CET 2005

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


On Thu, Dec 15, 2005 at 11:22:32AM +0100, Lars Ellenberg wrote:
> / 2005-12-14 19:51:04 +0100
> \ Christof Amelunxen:
> > Hi,
> > 
> > Lars Marowsky-Bree wrote:
> > > On 2005-12-14T18:59:29, Christof Amelunxen <ca at ordix.de> wrote:
> > >>
> > >> 1. NodeA (P) --- NodeB (S)   # everything ok
> > >> 2. NodeA (P) - - NodeB (S)   # DRBD detects connection loss, goes WFC
> > >> 3. NodeA (P) - - NodeB (S)   # Linux-HA detects split brain, A kills B
> > >> 4.   /       - - NodeB (P)   # NodeB takes over, goes primary
> > >>
> > >> There have been writes on NodeA between step 2 and 3. These are lost
> > >> after
> > >> Linux-HA has killed A and made B primary. I know the best solution is to
> > >> avoid this situation by any chance and we are using serial heartbeats,
> > >> too, but what if it happens anyway?
> > >
> > > The writes are lost.
> > 
> > Does that mean in this case automatical failover without any human
> > intervention is not possible at all if data loss is unacceptable?
> 
> In short, yes.
> 
> In DRBD 8 we can avoid this.
> NodeA will block writes right at 2., and trigger a callback.

Clearly I've guessed badly at what drbd 0.7 does, sorry for the confusion.

Could I get you to elaborate on what Protocols A,B and C do in drbd-0.7
and in relation to connection loss ?

Regards,
Paddy
-- 
Perl 6 will give you the big knob. -- Larry Wall



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