[DRBD-user] DRBD + Heartbeat + 1 eth + 1 serial

Lars Ellenberg lars.ellenberg at linbit.com
Fri Sep 28 16:21:36 CEST 2007

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, Sep 27, 2007 at 01:06:39PM +0200, Matteo Campana wrote:
> Hi Lars and all the guys in ML :).
> My problem is to understand the behaviur of my HA system: I have read in 
> the documentation about heartbeat that at least 2 channels of 
> communication between 2 nodes are required to preserve the system from 
> the "split brain" problem (in my system I have 1 ethernet +  1 serial).
> But....in my tests I see however  that DRBD says the "infamous" :) 
> message "split-brain detected" ecc.. .
> My test:
>    * I disconnect primary node from the ethernet
>    * secondary ----> primary  (ok)
>    * I reconnect primary
>    * secondary still remain primary (ok for my config)
>    * the problem is that the two nodes are standalone and not
>      re-syncronize theirs drbd partition.
> DRBD does not use also the serial channel in order to communicate 
> between the nodes?

um. it does use the heartbeat communication infrastructure,
if you configure the "outdate-peer handler", in which case it had
outdated the other node, before you try to make it primary,
thus preventing you from going online with stale data.

or did you just suggest that we should mirror block io
via 9600 baud serial line?

> And if does not,  there is  a lack of documentation :)

send in some patches for the manpage, please.

even patches just inserting lines with
 "FIXME I don't understand this" or
 "FIXME please clarify"
will help to point out what you think needs to be improved.


: Lars Ellenberg                            Tel +43-1-8178292-0  :
: LINBIT Information Technologies GmbH      Fax +43-1-8178292-82 :
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