Here let me help Keven out as he wanted to place his trophy on our response (yes should have been better but without the blood).

Here is a better description and using Protocol C is better in the end. If you don’t like it build it yourself .

For each device, drbd will (try to) allocate X MB of bitmap, plus some constant amount (<1MB). X = storage_size_in_GB/32, so 1 TB storage -> 32 MB bitmap.

By default Linux allocates 128MB to Vmalloc. For systems using more than 4TB, this may cause an issue - but give us time as we resolve this!!! It will happen, we are not going to just update without hard testing with our main customers unlike what some want it now.