New system, higher active connections?

[Roberto Nibali]

> We just moved our primary load balancer from an ancient Dell PowerApp 
> 120 running Red Hat 7.3 to a newer Dell PowerEdge 750 running Fedora 
> Core 5.  However, we're noticing something weird.

Was 7.3 with 2.4.x kernel?

> Where before, we were seeing Active Connections in the 1-4 range even 
> during normal usage, we're now seeing them in the 12-16 range on 
> average.  We've got the same weighting on the new server as we did on 
> the old.

Different Server system and most importantly, different software 
configuration. IPVS between 2.4 and 2.6 (provided my assumption above 
holds) has change significantly with regards to the ratio of 
active/inactive connections. We've seen that in our rrdtool/MRTG graphs 
as well.

> Does anyone have any ideas why we might be seeing such a jump on this 
> newer system?

Different kernel, where at least for the (w)LC scheduler the RS 
calculation is done differently. On top of that, the TCP stack has 
changed tunables and you hardware also behaves differently. The LVS 
state transition timeouts are different between 2.4.x and 2.6.x kernels, 
IIRC and so, for example if you're using LVS-DR, the active connection 
to passive connection transition takes more time, thus yielding a 
potentially higher amount of sessions in state active connection.

We'd need more information if you want to dig this phenomenon.

Best regards,
Roberto Nibali, ratz
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