[DRBD-user] split brain recovery -- after-sb-0pri

Florian Haas florian.haas at linbit.com
Tue Feb 19 19:55:43 CET 2008

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


Doug,

automating split brain recovery is something you ought to consider very very 
carefully. Depending on the application, it may be totally unacceptable to 
automatically recover from split brain using one of the after-sb-* options. 
Automatic recovery from split brain always discards modifications made to the 
data on one node in some form or another, without asking.

The recommended way of handling things in DRBD 8.2 is to leave the split brain 
recovery settings at their defaults (disconnect) and implement a split brain 
handler that emails or pages operators (handlers section, split-brain 
option -- see the drbd.conf man page). Then intervene manually to resolve 
split brain.

And, of course, prevent split brain in the first place: use redundant 
heartbeat links, make one link independent of powered networking components 
(read: use a crossover cable), use dopd.

Hope this helps,
Florian

On Friday 15 February 2008 20:47:28 Doug Lochart wrote:
> I have encountered a split brain scenario while following a tutorial.
> I have been looking at the various options for the *after-sb-0pri*
> parameter and have a couple of questions.  With some help from the
> linux-ha list I now see that following the tutorials was not such a
> good thing to do because the tutorials failed to mention anything
> about split-brain, stonith, or fencing.  The next incarnation of my HA
> cluster will use STONITH (ipmi) to help with the split brain
> phenomenon.  I need to do some more work (learning) in this area but I
> see that drbd has a parameter that deals with split brain recovery at
> least at its own level.  My question to all is do I have to take into
> consideration what I do in the HA world (Stonith etc) when I set the
> *after-sb-0pri* parameter or are the two non intersecting?
>
> thanks!
>
> regards,
>
> Douglas Lochart

-- 
: Florian G. Haas 
: LINBIT Information Technologies GmbH
: Vivenotgasse 48, A-1120 Vienna, Austria

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