in 20 years of doing SIEM and SIEMlike solutions, I've yet to find an engagement that said 'Oh, yes...our volumes are XX and YY'...mostly it's a /shrug and a less than educated guess.
There's even reluctance to turning things on and _watching_ it for 10 minutes. An activity that would immediately give you a much better idea of volume. Folks just don't like doing it.
Then you get the things were setting up a redundant logsource is just unwise. DNS logging was 2 orders of magnitude greater than everything else a SIEM was doing. And Email was about the same size.
There's even reluctance to turning things on and _watching_ it for 10 minutes. An activity that would immediately give you a much better idea of volume. Folks just don't like doing it.
Then you get the things were setting up a redundant logsource is just unwise. DNS logging was 2 orders of magnitude greater than everything else a SIEM was doing. And Email was about the same size.