[ClusterLabs] Antw: Re: Antw: Re: design of a two-node cluster

[Ulrich Windl]

>>> "Lentes, Bernd" <bernd.lentes at helmholtz-muenchen.de> schrieb am 16.12.2015 um
13:31 in Nachricht
<1496952480.528507.1450269100369.JavaMail.zimbra at helmholtz-muenchen.de>:
> Ulrich wrote:
> 
> ----- On Dec 16, 2015, at 8:36 AM, Ulrich Windl Ulrich.Windl at rz.uni-regensburg.de 
> wrote:
> 
>>>>> "Lentes, Bernd" <bernd.lentes at helmholtz-muenchen.de> schrieb am 16.12.2015 um
>> 00:35 in Nachricht
>> <1621336773.386234.1450222516246.JavaMail.zimbra at helmholtz-muenchen.de>:
>> 
>> [...]
>>> What is about a quorum disk ? I also read about "tiebrakers" or that STONITH
>>> is magically able to chosse the right
>>> node to fence (i can't believe that).
>> 
>> If you read "the right" as "not both" it's OK ;-)
>> 
>> In HP Service Guard they used a "lock disk" (SCSI disk) as tie breaker: On 
> split
>> brain every node tried to "SCSI reserve" the unit, which only one node
>> suceeded. Then (in an SBD like manner) the name of the survivor was written 
> on
>> to the disk (I guess), and every other node committed suicide (that's 
> different
>> from STONITH where external nodes kill another, AFIK). Something like that 
> is
>> still missing.
>> 
>> Personal note: Bernd, I think it's time to try things now. You discussed a 
> lot,
>> but I still think you never tried the proposals...
>> 
> Yes, you are right. But i like to have an idea of what will i do before, 
> rather than testing "which design do i want to have ?"
> It will still remain a lot to test.

Yes, you are right: As J. W. Goethe wrote "Grau ist alle Theorie" ("all theory is grey") some things work differently in practice than in expectation ;-)

> I just have to wait for the second HP server we will order in january.
> We are a public institution and orders sometimes require a lot of time. You 
> work at an university, maybe you experience the same ...

Sometimes the trick is to keep a bunch of old hardware or fetch it from the recycle bin (for testing only, of course) ;-)

Regards,
Ulrich