On Sun, 2009-06-07 at 22:25 +0200, Alan DeKok wrote: > Karl Auer wrote: > > DHCP failover and load-balancing are not simple *at all*. > > As evidenced by the fact that the ISC fail-over protocol is horrible, > and the implementation is almost as bad.
Oh, I'm 100% with you on that. > Oh, and the server is O(N^2) in the number of leases. Why? Well... > they don't use fancy concepts like "dynamically resizable hash tables". True, but that's ISC's implementation. I use Nominum's DCS, which starts in seconds regardless of the number of leases, largely because it has a database backend (but not distributed or HA - highspeed, local and dedicated) and which is completely dynamically configurable. Nothing short of upgrading the server requires it to be stopped. And with one major exception (which was a *bug*), failover as implemented by Nominum has never, ever let us down. Let's not confuse the protocol with the implementation. > It's really not that hard. Database books describe replication > protocols. They look very different from the DHCP fail-over protocol. Though to be fair, database replication is *not* solving the same problem as failover is. Failover allows independent entities to maintain the same view of the data, and a view with severe constraints. The real mistakes were made defining DHCP itself, but for the time they did an OK job. > And for most enterprise sites, you *don't* need a fail-over protocol. > Really. Well... if they have a HA arrangement for DHCP such as that described here recently, maybe not. Otherwise we'll have to disagree on that. Regards, K. -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Karl Auer (ka...@biplane.com.au) +61-2-64957160 (h) http://www.biplane.com.au/~kauer/ +61-428-957160 (mob) GPG fingerprint: 07F3 1DF9 9D45 8BCD 7DD5 00CE 4A44 6A03 F43A 7DEF
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