[OpenAFS] Serious trouble, mounting /afs, ptserver, database rebuilding

Stephan Wonczak a0033@rrz.uni-koeln.de
Tue, 29 Jul 2008 10:56:43 +0200 (CEST)

   Hi Brandon!

On Tue, 29 Jul 2008, Brandon S. Allbery KF8NH wrote:

> On 2008 Jul 29, at 3:44, Stephan Wonczak wrote:
>> While more redundancy (i.e. a third database server) is always a good idea, 
>> it is not strictly necessary, much less 'a bad idea to run with two 
>> database servers'.
>> Christof probably was thinking about the 'split brain' problem, which does 
>> not come into play with the AFS architecture; we are proof against that 
>> one. I made a posting about this a while ago; it should be in the archives.
> Actually he's thinking about a screw condition that used to happen with 
> voting for a sync site if you have 2 database servers and the 
> lower-IP-numbered one goes missing.  I *think* it has been fixed now.

   Not really a bug. If the lowest numbered DB server goes AWOL the 
remaining server has no chance to become master. I cannot distinguish 
(without human help) wether there is a simple communication problem or if 
the lower server really is down. So it stays in RO-Mode, as it should.
   As an admin you then have the choice to go back to a single-server 
scenario, or bring the other one back online. I do agree however that this 
is not too nice, and you are probably better off with three DB servers.

 	Dipl. Chem. Dr. Stephan Wonczak

         Zentrum fuer Angewandte Informatik (ZAIK)
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