Kdump space requirements
 

I have a 2 CPU server, with 40G of ram. I have set up kdump to dump a vmcore to another system in the /cores filesystem.

My question is..

What is the minimum amount of space /cores must be to hold a vmcore dump from my 2 CPU system?

Is it 40GB, the amount of total ram of the system?

Or 80GB, 40Gx2, the total ram times each CPU?

Diskdump tells you in /var/log/message (or used to) - slightly more than your installed RAM. Allow for more than one ...
Have a look at this for options on saving some space with kdump. Also tells you how to force a panic - should give you something to work with.