so you mean to say that efi  based image can’t be restored bios based hardware?

[RS] Yes. You are right

 the bare metal backup  is only required  if you want restore the image to another fresh uefi supported system ?

[RS] BMR can be done in case of current hardware failure or to an alternate machine  supporting same boot configuration

 system state is enough in case of  same kind of hardware failure?

[RS] System State will only protect system specific data which includes the registry, COM+ class registration and boot and system files as well as the certificate and AD databases if applicable. It will not be able to bring up your system in case of hardware failure. BMR is the solution to come back from hardware failures.

How frequent the backup should be taken in case of cluster  node?

[RS] BMR will be able to recover only current system and data on current server. It is a one-node solution. So whether it is a cluster-node or not, you can set up a the frequency of you backup based on the data churn on the current server.

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