[ClusterLabs] Stonith

[Antony Stone]

Hi.

I have a 7-node corosync / pacemaker cluster which is working nicely as a 
proof-of-concept.

Three machines are in data centre 1, three are in data centre 2, and one 
machine is in data centre 3.

I'm using location contraints to run one set of resources on any of the 
machines in DC1, another set of resources in DC2, and the DC3 does nothing 
except act as a quorum server in case DC1 and DC2 lose sight of each other.

Everything is currently on externally-hosted virtual machines (by which I 
mean, I have no access to the hosting envorinment).

I now want to implement fencing, and for the PoC VMs I plan to use 
external/ssh in order to reboot a problem server - once things move to real 
hardware we shall have some sort of IPMI/RAC/PDU control.

Reading https://clusterlabs.org/pacemaker/doc/crm_fencing.html it seems that I 
define this just the same as any other resource in the system, however it's not 
clear to me how many resources I need to define.

When a machine needs restarting, any other machine in the cluster can do it - 
all have public-key SSH access to all others, and for IPMI/RAC/PDU every 
machine will have credentials to connect to the power controller for every 
other machine.

So, do I simply create one stonith resource for each server, and rely on some 
other random server to invoke it when needed?

Or do I in fact create one stonith resource for each server, and that resource 
then means that this server can shut down any other server?

Or, do I need to create 6 x 7 = 42 stonith resources so that any machine can 
shut down any other?

Thanks for any guidance, or pointers to more comprehensive documentation.


Thanks,


Antony

-- 
BASIC is to computer languages what Roman numerals are to arithmetic.

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