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From Bill Stoddard <b...@wstoddard.com>
Subject Re: Working on some load balancing methods
Date Tue, 11 Jan 2005 14:27:43 GMT
Jeffrey Burgoyne wrote:
> I'm using least connections with an Alteon on a recently installd system.
> Least connections, whil eperhaps crude, is one of the most effective
> methods for load balancing.
> 
> The general reason is that over the long haul, it will be putting
> conenctions onto those mahcines which are discharging their old
> connections faster. That is usually due to better performance, althoguh
> not always.
> 
> We have run into issues with more "intelligent" load balancing that kept
> pumping up one machine more than others because its CPU load was low. In
> fact there was a disk issue which kept the machine in a bad IO wait state
> which was not taken into account, hence most of the connections went to a
> "slower" machine.
> 
> In playing aorund with the various types of laod balancing, I came to the
> conclusion that the KISS principle applied. More intelligent load
> balancing is probably better, but in all honesty its splitting hairs. If I
> can get 98% of my connections going to the best machine, why work harder
> to get to 99%? And also remember, just because it doesn't get to the best
> machine does not mean it will get done that much faster. Maybe 3 seconds
> instead of 2? Not worth the effort in most cases.
> \
> IMO if you ever get to the case where a machine is simply way to busy to
> handle the load, you need to add more hardware. Thats a much better
> investment instead of trying to squeeze every last drop of performance out
> of a system, at least for a larger organization where time is money.
> 
> One caveat on least connections though, it would be nice if it was a
> weighted least connections average where you could target a percentage of
> connections to every machine. I've got one J2EE back end system needing to
> be load balanced now where one machine is a 4 year odl Sun 450 and the
> other is a newer V880. In an ideal world I want 70% of the traffic to the
> V880. Least connections will get me close to that, but not all the way.
> 
> Jeffrey Burgoyne

+1

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