httpd-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Jeffrey Burgoyne <burgo...@keenuh.com>
Subject Re: Working on some load balancing methods
Date Tue, 11 Jan 2005 12:03:52 GMT
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

Chief Technology Architect
KCSI Keenuh Consulting Services Inc
burgoyne@keenuh.com

On Mon, 10 Jan 2005, Stefan Hueneburg wrote:

> Hallo,
>
> Jim Jagielski <jim@jaguNET.com> wrote:
>
> > I'm currently working on code that extended the lb method
> > within the 2.1/2.2 proxy from what is basically a
> > weighted request count to also be a weighted
> > traffic count (as measured by bytes transferred)
> > and a weighted "load" count (as measured by response
> > time). The former is further along and the methods
> > will be selectable at runtime... This is definitely
> > a scratch I'm itching, but before I spend too much
> > (additional) time on it, I'd like some feedback
> > on whether the concept is one we can all get behind.
>
> Maybe "least connection count" is also interesting.
>
> However, on Alteon-LB i experienced some kind of weird load pumping
>  when i used "least connection" mode.
>
> Bis dann,
> Stefan H√ľneburg
> --
> easynet GmbH (http://www.de.easynet.net)
> System Administrator, Application Services
> Harburger Schlossstrasse 1, D-21079 Hamburg
> fon: +49-40-77175-526, fax: +49-40-77175-519
>

Mime
View raw message