[ClusterLabs] Antw: Re: Antw: Re: Antw: [EXT] Stonith failing

[Andrei Borzenkov]

18.08.2020 10:35, Ulrich Windl пишет:
>>>> Andrei Borzenkov <arvidjaar at gmail.com> schrieb am 18.08.2020 um 09:24 in
> Nachricht <83aba38d-c9ea-1dff-e53b-14a9e0623d9d at gmail.com>:
>> 18.08.2020 10:10, Ulrich Windl пишет:
>>>>>> Ken Gaillot <kgaillot at redhat.com> schrieb am 17.08.2020 um 17:19 in
>>> Nachricht
>>> <73d6ecf113098a3154a2e7db2e2a59557272024a.camel at redhat.com>:
>>>> On Fri, 2020‑08‑14 at 15:09 +0200, Gabriele Bulfon wrote:
>>>>> Thanks to all your suggestions, I now have the systems with stonith
>>>>> configured on ipmi.
>>>>
>>>> A word of caution: if the IPMI is on‑board ‑‑ i.e. it shares the same
>>>> power supply as the computer ‑‑ power becomes a single point of
>>>> failure. If the node loses power, the other node can't fence because
>>>> the IPMI is also down, and the cluster can't recover.
>>>
>>> This may not always be true: We had servers with three(!) power supplies
> and 
>> a
>>> BMC (what today is called "light-out management"). You could "power down" 
>> the
>>> server, while the BMC was still operational (and thus could "power up" the
>>> server again).
>>> With standard PC architecture these days things seem to be a bit more
>>> compicated (meaning "primitive")...
>>>
>>
>> BMC is powered by standby voltage. If AC input to all of your power
>> supplies is cut off, there is no standby voltage anymore. Just try to
>> unplug all power cables and see if BMC is still accessible.
> 
> Of course! What I tried to point out is: With a proper BMC, you DON'T need to
> cut off the server power.
> 

You seem to completely misunderstand the problem - if external power is
cut off, it is impossible to stonith node via IPMI because BMC is not
accessible.