Developing Mars lander software

[Tolga Cakiroglu]

On Wednesday, 19 February 2014 at 01:09:43 UTC, Xinok wrote:
> On Wednesday, 19 February 2014 at 00:16:03 UTC, Tolga Cakiroglu 
> wrote:
>>
>> TL;DR the link though, how are they detecting that a CPU 
>> fails? An information must be passes outside of CPU to do 
>> this. The only solution comes to my mind is that main CPU 
>> changes a variable on an external memory at every step, and 
>> back up CPU checks it continuously to catch a failure 
>> immediately. But this would require about 50% of CPU's power 
>> already.
>>
>> While thinking about this kind of back up systems, knowing and 
>> reading that some people are really doing is really great.
>>
>
> I'm assuming this has something to do with it:
> https://en.wikipedia.org/wiki/Heartbeat_%28computing%29
>
> In clustered servers, the active node sends a continuous signal 
> indicating it's still alive. This signal is referred to as a 
> heartbeat. There's a standby node waiting to take over should 
> it stop receiving this signal.

I think only knowing that it has failed is not enough. Because 
the process is landing, and other CPU should know where the 
process is left. With that heatbeat signal, only option is that 
all sensor information must be sent both CPUs continuously and 
sensor values should be enough about what next step to be taken. 
Then I think it can continue the process flawlessly.