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From Klaus Wagner <kl...@it-austria.net>
Subject Re: load balancer "cluster" set
Date Mon, 07 Aug 2006 11:48:15 GMT
> Load balancing really belongs at the network layer.
depends on your needs
> 
> IBM released free load-balancing software for linux and windows about
> 1997.  My former employer's integration group (about 3 people) got a
> fully redundant implementation running (on 4 pcs) in about 4 months.
ack
> 
> The company abandoned the free s/w version for hardware implementations
> on Cisco gear (and others) within about 6 months.  I'm sure the price
> for proprietary hardware has dropped substantially since then.

disagree the price is still at the same level (just the releases went 
up)

I also disagree when it comes to the point of Cisco has the perfect LB
solution. In fact they have not. The problem is not the distribution,
which is not able to provide a Load distribution in means of spreading
EQUAL load on some servers because

a) most applications need application stickyness
b) neither round robin nor other implementations manage to keep equal
load on servers because they can't measure the SERVERS load

But again problems are elsewhere. There are quite some methods
to provide stickyness. All fail in some kinds of uses. They can't watch
cookies 100% correctly and if they are told to introduce their own, they
mess up the protocol. IP stickyness has issues when upstream proxies are
used in a balanced way.

Finally ssl stickyness is not working correctly too (which is generally
a bad idea anyway).

But there is a solution: lose your capeablity of handling ssl and source
that out to cisco appliances completely.

Finally to clean up with myths: The loadbalancing in ciscos LBs is NOT
done in hardware. In fact they use multi purpose CPUs to do LB
decisions. Only when it comes to plain routing, that happens in
hardware.

On the other hand ... to be nice to cisco ... they have done a great job
to keep this thing stable. Servers crash far more often than these
appliances. And they have done a great job in means of failover from one
lb to another because they use routing protocols to announce the active
lb way faster that taking up an ip address on a server and starting a
software lb.

so ... there are reasons to use appliances and there are reasons not to
use them (flexible balancing, application layer stickyness, and so on)

regards klaus


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