Failover on a large DHCP system

Frank Bulk frnkblk at
Sat May 9 04:26:05 UTC 2009

You could do both -- use omshell to make the changes, but also update
dhcpd.conf.  That way you have the benefit of instant change without reload
and the security of a configuration file.


-----Original Message-----
From: dhcp-users-bounces at
[mailto:dhcp-users-bounces at] On Behalf Of Nicholas F Miller
Sent: Friday, May 08, 2009 12:01 PM
To: dhcp-users at
Subject: Re: Failover on a large DHCP system

> On Fri, May 08, 2009 at 10:09:29AM -0600, Nicholas F Miller wrote:
> > With constant restarts of DHCP and the need for
> > failover to redistribute the pools on restarts I think the server  
> load and
> > disk access would be too high.
> The disk access footprint between failover restarts is only the
> "changes" to the database.  It doesn't remirror the lease db every
> reconnect - they only update each other with any new bindings that
> ocurred during the blackout.
> With huge numbers of leases, it can be a problem however, as it causes
> both servers to traverse the entire lease database (in memory) right
> now.

With around 72,000 leases at any given time and 677 pools, should we  
just continue using our current restart methodology or try to  
implement omshell as a way to add/remove the hosts? Since omshell  
writes its changes to the leases file, the changes will survive a  
restart, ignoring the config. This could lead to some interesting  
troubleshooting if something were to go awry.

Nicholas Miller, ITS, University of Colorado at Boulder

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