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From Sergei Babovich <sbabov...@demandware.com>
Subject Re: Achieving quorum with only half of the nodes
Date Thu, 15 Jul 2010 18:22:08 GMT
Thanks, Ted.
This would solve power feed problem. Unfortunately we have similar 
situation with the switches. Failure of one will bring half of the 
servers down. It is understood that changing/adjusting hardware 
infrastructure can solve the problem. Unfortunately this is not under my 
control. So I am trying to explore possible options (I understand that 
there is no currently available solution out of the box) within existing 
conditions.

On 07/15/2010 01:56 PM, Ted Dunning wrote:
> A small rack mounted UPS doesn't require a full-scale rebuild of
> infrastructure and would get you through almost all power fail scenarios.
>   If you have 5 ZK servers, put 3 on one power source and give one of them
> the UPS.  Then give put the other 2 on the second power source.  If power
> source A fails, you keep 2+1 servers and if power source B fails, you keep
> 3.
>
> If you can stand manual intervention during an emergency, you might be able
> to devise a recovery scenario.  You can put 3 and 2 on A and B as above
> without a UPS.  If B fails, you are fine.  If A fails, you can go in and
> reconfigure the remaining nodes to only consider themselves as the quorum.
>   This is not a good plan in general because ZK is reliable enough that
> people forget about it.  That means it won't be top of mind in a disaster
> response.
>
> On Thu, Jul 15, 2010 at 10:30 AM, Sergei Babovich
> <sbabovich@demandware.com>wrote:
>
>    
>> Three power sources obviously would solve the problem. Unfortunately at
>> this moment it does not seem to be feasible (we will need to rebuild the
>> whole existing infrastructure).
>>      

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