Help me understand this a bit...

Scott Morris scottmmorris at
Fri Mar 2 10:38:00 MST 2007


I have noticed something peculiar that is adversely affecting the
performance of our production server.  I am not really sure where to
start with this one.

Network topology is your basic class C 192.168.0.x subnet, desktop IPs
are dynamic, server IPs are static.

We have a production server that is exhibiting some strange behavior. 
We'll call this machine SERVER A.

>From my desktop machine, I can connect via SSH very quickly.  From my
co-worker's machine, it always takes 20 seconds to connect via SSH. 
>From a different co-worker's machine, he connects directly to the MySQL
server running on SERVER A.  This connection also takes several seconds
to establish.

What is strange is that when I connect via SSH, it is immediate.  Also,
if I do a connection to the database server running on that same machine
via PHP from a second server (SERVER B, for example), it has no trouble
whatsoever connecting immediately.

I wrote a script to test the connection from SERVER B to the MySQL
server on SERVER A.  It connects, runs a small query, and receives the
result.  It then tells me how long it took for this to occur.  I put it
in a loop which repeats every two seconds.  So every couple of seconds,
it connects, runs the query, returns the result, and displays the time

I noticed that exactly every 120 seconds, it would take 20 seconds to
run the query.  All other queries were executed in far less than one second.

Apologies if this is something obvious, but I'm not super sure what
would be the most effective way to approach this particular problem. 
Any suggestions would be greatly appreciated.  As somewhat of a
masochist, I can also appreciate a well-executed insult.

Thanks, peace out.

Scott Morris

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