On Mon, 23 Jul 2007, Harald Tveit Alvestrand wrote:
>
> I'm sorry, but I do not understand....
>
> in what context is 277 operations per second a large number?
> AFAIK, a REFRESH operations (for no zone change) is a lightweight operation.
Its a fairly high number of transactions per second for DNS servers
backed by databases. Especially when you suppose that is just the zone
checking, and not actual queries for the "real content" records. The
content queries (that is, the A records, etc guts in the zones that
people want) would raise the TPS by orders of magnitude. The zone
checking would still be a (relatively) small number compared to
everything else.
However, a million authority zones on a single server is probably also
unrealisticly high. No one has that many zones on one server. I'm
somewhat dubious of the claim that there are 50,000 zones on a single
server. 50,000 zones in one hosting provider doesn't surpise me. Of
course, if they use something like powerDNS with database backing, all
zones _can_ appear on every server. But it would seem a poor idea to do
that, at some point.
Database backed systems have the advantage that they don't need to do
zone transfers, but can use database replication behind the scenes.
I've even seen people put cache data in databases. I found this while
searching for anycast recursive servers. [yes, that also means that
anycast clones can be detected, meaning stateful anycast isn't stable,
since if TCP "detects" two servers with the same IP address, the
connection fails.]
Anyone who did have a million zones, I think, wouldn't have it on a
single server. Or, if they did, would have some better way to improve
their transaction rates. I can think of a few ways, but none that
require protocol changes. I'll have to look into this draft more
closely.
--Dean
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