max-ixfr-ratio introduced with 9.17.0 sounds like a workaround instead
of a bugfix.
Anyway, can you recommend a sensible settings? I.e. when does the
performance problem of "large" IXFR starts to happen? Does this depend
on the ratio of the IXFR-size to zone-size, or does it depend on the
size of the IXFR, regardless how big the zone is? (I hope the first
thing, otherwise it would be better to define a max-ixfr-size instead of
I would like to know in more detail when the peformance drop happens, to
find a proper value for the max-ixfr-ratio. Or do I have to play around
with the value to find a compromise fast updates vs IXFR-triggered DoS?