DHCP Performance (was: Large leases file and long startup time)

[Alan Buxey]

Hi,

> server (yes, singular) supports a network with approx. 15,000 users, all
> DHCP'ed. During peak times (usually once or twice a day), we see upwards
> of 2-3k requests in a 15-30 minute interval.

yes...

> We've been running DHCPerf
> (http://www.nominum.com/services/measurement_tools.php) against a
> testing box, and we're seeing pretty poor performance - something on the
> order of only 1 request per second being handled within a 4 second window.

ummm, either I say ouch or I say are you sure you ran it right?  If you run
it on a system that cannot get DHCP or isnt working thats the sort of
result you see.   run eg tcpdump on your test server and see if you can see
the requests coming from that DHCPerf client - when I last ran it on some
running,loaded servers, I was seeing at least 120 requests per second
as the output... its a neat tool by the way. great for testing

> Does anyone else out there have an idea of the load that their dhcpd
> instance is handling? Has anyone else with sustained loads around 1-3
> RPS had issues? Is anyone else running something on the order of 400+
> subnets and 10000+ clients?

yes - could I suggest that you increase your lease time for certain
subnets where you dont expect/need address churn - eg 86400 seconds ?

what do you get when you check system performance eg IO stats... DHCP
is very IO intensive and something else churning your disks up wont help.
you could always eg keep the leases file in seperate disk...or in shmem
(but ensure you write it out frequently to a stored location!)

alan