DNS Cache, database backends...

[Jim Reid]

>>>>> "James" == James Raftery <james-bind-users at now.ie> writes:

    James> On Wed, Feb 07, 2001 at 09:33:48AM +0000, Jim Reid wrote:
    >> Who's to say what data in the cache dump file is valid when the
    >> server read in this file at startup (assuming it could)?

    James> The zone administrator who set the TTLs says how long data
    James> remains valid. When the data is read by the nameserver as
    James> it starts it discards records whose TTLs have expired and
    James> keeps the rest (assuming it could).

Yes but that assumes that any time stamps indicating when this
hypothetical dump file was created and loaded are correct. ie that N
seconds really have elapsed between those two events. This isn't
always as straightforward as it should/could be. Some computers are
bad at timekeeping. Just look at the number of questions on this list
about failed TSIG validations because clocks weren't synch'ed. If this
feature came to pass, I can envisage clueless DNS admins copying these
files from server to server and then whining because the restored
caches are not the same because the server's clocks don't keep the
same time. And to repeat what I said earlier, the easy way to solve
this "problem" is simply to leave the name servers alone and only stop
and start them when it's really necessary: for example when installing
new name server software.

This discussion about preserving caches is just silly. It's a bit like
expecting the entire contents of your computer's RAM or the state of
every CPU register to be preserved after the system has been power
cycled. Sure it could be done, but what's the point? Really.