[f-nsp] Load balancing DNS servers on a ServerIron 8XL

p.ramesh p_ramesh at rocketmail.com
Wed Sep 27 19:21:45 EDT 2006


Yeah, that's true. Sorry, I overlooked. One problem could be that DNS1 is failing healthchecks. Check logs. 
  
  Check the session table for any long-standing session. Default udp  session-age is 5 minutes. So, a session will start at age 57 and ageout  at 62. Check if there are any session stuck in the table with age 58 to  61.
  
  Thanks,
  Ramesh
  
  

Tom Samplonius <tom at uniserve.com> wrote:  
   Actually, it is fairly clear that the original poster is already using 
round-robin.


Tom


On Wed, 27 Sep 2006, p.ramesh wrote:

>  That's because you have the default load-balacing predictor as  least-connection ( you wont see in the config, because this is default).
>
>  dns connections are usually short-lived, connections get closed pretty  fast. First connections goes to DNS2. by the time second connections  comes, there are no existing connections on any of the 2 servers, so  Foundry decided to forward the request to DNS2 because of  least-connection predictor. least connections looks at currently how  many total number of connections are handled by any server
>
>  Now, configure "server predictor round-robin", you are at peace and see  both servers taking equal number of connections. round-robin is dumb,  first connection go to DNS1, next time go to DNS2, third request take  it to DNS1, and fourth one goes to DNS2.
>
> Foundry is  coming out with powerful ServerIron 4G(read 4 Gig ports) with SSL  support, better upgrade to that, its pretty cheap.
>
>  -Ramesh
>
>  Hope
> Tom Samplonius  wrote:
>
> DNS2 might be too slow to respond, or lost a few hundred requests.
>
> From reading the docs, the SI has special handling for DNS requests. It
> removes the connection immediately after the response is processed. So if there
> is no response, the connection will stay around until it is aged. So if DNS2
> just discarded a bunch of requests, they would sit around as connections.
>
>
> Tom
>
>
> On Wed, 27 Sep 2006, Drew Weaver wrote:
>
>> Howdy list, been using foundry load balancers for quite some time.
>> I'm having a hard time understanding one issue.
>> pertinent config:
>>
>> server real DNS1 10.1.0.2
>> port dns
>> !
>> server real DNS2 10.1.0.3
>> port dns
>>
>> server virtual DNS 192.168.0.89
>> predictor round-robin
>> port dns
>> bind dns DNS1 dns DNS2 dns
>>
>> pretty straightforward right?
>>
>> OK, well I was looking at the real server stats and I noticed that DNS1
>> had 37 active connections whilst DNS2 had 781 active connections all of
>> the servers/pcs/devices are set to use 192.168.0.89 as their resolver,
>> so why is there such a hugely unproportinate number of connections
>> hitting DNS2?
>>
>> Thanks!
>>
>> -Drew
>>
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