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Re: Server slowdown...



On Mon, 12 Apr 2004 10:00, Joe Bouchard <joe@bouchard.com> wrote:
> In a meeting at work (I'm part of the IT group at a large corporation)
> someone mentioned a particular kind of network hardware which would stop
> working correctly after a while.

Here are some ways that network issues can slow down a server:

On shared media (such as 10base2) accidentally leave an interface in 
promiscuous mode (there used to be a bug in tcpdump whereby running two 
copies of it at the same time could cause the interface to remain in 
promiscuous mode after both copies had exited).  A moderately busy 10base2 
could destroy the performance of a decent 1995 server machine if an interface 
was in promiscuous mode, and as the CPU use occurred in interrupt context 
none of the usual tools would tell you what was happening.

Send lots of minimal size packets to a server or to the media broadcast 
address.  Until recently minimal size packets on 10Mb media could destroy the 
performance of most systems.  Now with Gig-E even using 1500 byte packets you 
can destroy the performance of most systems.

If you had a router break and repeatedly send a single IP datagram to your 
server on a Gig-E link then the likely result would be a dramatic loss of 
performance.

If you suspect this then the best thing to do is run a program to measure 
system performance on the console and unplug the network cables.

-- 
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