Performance issue ( maybe )

Bjarne Blichfeldt bjb at
Tue Sep 7 07:58:07 UTC 2010

ok the plot thickens..

> -----Original Message-----
> From: Glenn Satchell
> Sent: 6. september 2010 15:09
> To: Users of ISC DHCP
> Subject: Re: Performance issue ( maybe )
> Ok, so this looks like some sort of networking issue, perhaps NIC,
> cables or switch port? Check you have up to date drivers for your NICs.
> Run ifconfig and look for any errors or collisions. Check the speed and
> duplex settings for the NIC and ask the network guys to check the same
> settings on the switch port. Check cables are well seated in the server,
> and if you can, on the switch.
> Try an ftp of a largish (few 10s of megabytes) file between each of the
> servers and a third one to see if one works well and the other has some
> problems? This will help isolate the system and give you a nice test case.
> Good luck, but at least a problem has been found, now to fix it!

Agreed on checking the network, but so far everything seems to be in order, spanning tree, half/full duplex,
no errors on the interfaces, no one else having issues, ftp from dhcp1 to dhcp2 runs close to 100Mb. No abnormal traffic.

However, as Tom brought to my attention, there are an awful lot of pool balancing going on. So here is a thought:
what if the pool balancing creates so much load on the dhcpservice, that the failover connection is lost ? That will create a 
runaway situation.

The situation last week seems to have escalated after a configuration change. We do configuration changes by 
1. pushing a new config to the primary server, then restart dhcpd.
2. pushing a new config to the secondary server, the restrt dhcpd

In both cases, we get communications-interrupted.

My failover clause is :

failover peer "ipc-dhcp1-ipc-dhcp2" {
        port 647;
        peer address;
        peer port 647;
        max-response-delay 90;
        max-unacked-updates 20;
        mclt 1800;
        split 128;
        load balance max seconds 5;

That means defaults for :
min-balance 60;
max-balance 3600;

Tom Schmitt mentioned 2 hours, I assume min-balance time.

My initial tought is to increase our values to:
min-balance 1800;
max-balance 7200;

> regards,
> -glenn


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