[DRBD-user] DRBD: failover when sync connection dies?

Greg Haase haaseg at onefreevoice.com
Tue Dec 18 17:26:16 CET 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 Mon, Dec 17, 2007 at 10:55:02AM +0100, Martin Gombac wrote:
>> On 2007.12.13, at 18:24, Martin Gombac wrote:
>> >On 2007.12.13, at 17:42, Florian Haas wrote:
>> >
>> >>On Thursday 13 December 2007 13:45:47 Martin Gombac wrote:
>> >>>Hi,
>> >>>
>> >>>i have a simple fail-over heartbeat/drbd cluster set up. In each
>> >>>server there are two network cards. One for internet access (WAN)
>> >>>and one for internal communication and synchronization (LAN). If
>> >>>one  node looses internet connection (WAN) the other takes over all
>> >>>resources as expected, but this does no thappen with local
>> >>>connection (LAN) which is just crossover UTP cable.
>> >>>In case if local connection (LAN) fails, cluster does not migrate
>> >>>all resources to one of the nodes and just continues to work
>> >>>without synchronized drbd resources (amongst other things).
>> >>>
>> >>>My question is this:
>> >>>How can i make one node take over all resources if local crossover
> you don't want to.
> if your lan connection dies,
> and your lan connection was your replication link,
> then you don't have replication anymore,
> and so you would go online with non-current data.
> if currently your LAN connection is a direct "crossover cable",
> why would you think any clients would benefit from failing over?
> if you change to a switched LAN, and add a ping node,
> why do you think any clients would benefit from that?
> how can you be sure what component failed,
>  local NIC, cables, remote NIC, switch, driver, ...?
> what problem are you trying to solve?
>   I mean not "failing over when the LAN link dies".
>   please zoom out a little.
> from my point of view, it makes no sense to trigger a failover
> because the replication link dies. it would even be harmful.
> so don't do that.
> --
> : Lars Ellenberg                           http://www.linbit.com :
> : DRBD/HA support and consulting             sales at linbit.com :
> : LINBIT Information Technologies GmbH      Tel +43-1-8178292-0  :
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This speaks really to the question I posted earlier. I agree that you
wouldn't want to fail-over, but... When your sync connection dies, how do
you handle it?

How do you prevent the other node from trying to come and and creating a
split brain situation?

How do you get alerted that the sync is broken?

How do you recover?

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