Re: Second Snort instance killing performance

[Marc Norton <mnorton () sourcefire com>]

You might try to use 'vmstast 1' to monitor the context switches, 
interrupts, and memory swapping  for each process,  see how they differ 
when you run one snort versus 2 snorts.  Some versions of red hat 
kernels have in the past favored high context switching for a better 
user experience - versus low context switching for better application 
processing.  Another issue might be memory caps, make sure the 
snort.conf's don't allocate so much ram that your suing virtual; memory, 
otherwise performance will suffer.

Paul Melson wrote:

> I've just run into an interesting situation with one of my Snort sensors.
> I've added another interface attached to a new span port to my existing
> sensor box and I want to run a second Snort process for that interface.
> Same binary, same logs, but different config file and rule set for each
> process.  If either the original process monitoring eth1 or the new process
> monitoring eth2 are running, the load average is about 0.3-0.4.  If both
> processes run simultaneously, load jumps to 2.0+ and performance suffers,
> packets drop, etc.  
>
> The server is a Proliant G4 running RHEL4 with dual Xeon 3GHz CPUs, 2GB RAM,
> Ultra320 disks, etc. so it shouldn't be choking on this relatively small
> amount of traffic.  Snort version is Version 2.3.2 (Build 12).
>
> Anybody run into anything like this before?  The problem seems to be
> specific to running two Snort processes, but I'm not sure where to
> troubleshoot next.
>
> PaulM
>
>
>
>
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--
Marc Norton      Snort Team Lead
Sourcefire,Inc   410-423-1924
www.snort.org    www.sourcefire.com 



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