Scalability million addresses

[Christoph Weber-Fahr]

Hello,

> Got a customer who wants to use DHCP.
> 
> Would ISC DHCP be able to handle 2 million defined IP addresses with
> 500K active leases? What would be area of concern (bottlenecks etc)?
> Thanks

Not without some serious hacking.

Unfortunately, ISC DHCPd is very bad at administering large address
pools.

We did some intensive testing with those kinds of loads (pools of up
to a million addresses), and the results weren't pretty.

And that is not a problem of active leases - the absolute pool size
is the the performance relevant number.

For the moment we settled down on using several geographically
distributed(redundant pairs) of dhcpds for not more than 90k
addresses and do not expect such a pair to withstand a sustained
load of more than 60 qps.

With a singular (non redundant) system you'd probably get more in
the area of 200+ k addresses and ~100-150 qps.

Target hardware were vanilla HP servers wth Xeon 5150
processors.

Those numbers are admittedly a little on the conservative side,
but not that much.

We had someone profile that thing for us under load, and
apparently ISC dhcpd spends most of the time happily
micromanaging/sorting the whole address pool.

(BTW - if any of the ISC guys wants our load test
software capable of simulating that amount of devices,
I'd be happy to provide it)

Caveat - those tests were done on versions of dhcpd 3.0 and 3.1,
I have no data yet on 4.x.

Regards

Christoph Weber-Fahr