At 10:25 PM 1/29/99 -0600, Michael A. Stone wrote:
>> > this post has gotten long enough that i won't go into the gory
>> > details (those of you who bet that i *don't* know how to shut up
>> > can pay up, and face the terrifying concept that this is
>> > *voluntary* behavior.. ;-), but i'll be happy to provide details
>> > if you want them.
>>
>> Hey, if you don't have any nagging tendonitis, feel free....
>
>
>well, i'm thoroughly into rant mode at this point, so what the
>heck.
>
>the first piece of the puzzle is the Apache SSI system,
>specifically the directive:
>
> <!--#include virtual="filepath" -->
>
>this is the preferred way to include another file, or the output
>of an executable, in the current page. the filepath is
>restricted to the local machine, but you can work around that
>with the proxying system, which is the second piece.
Actually for a program, it would be
<!--#exec cmd="filepath" --> or
<!--#exec cgi="filepath" -->
[snip]
>
>what most people don't know is that it's perfectly legal to give
>more than one machine the same name in a DNS file. if my host
>file looks like so:
>
> remote.foo.com. IN A 10.0.0.100
> remote.foo.com. IN A 10.0.0.102
> remote.foo.com. IN A 10.0.0.103
>
>
>any request for 'remote.foo.com' will be sent equally to all
>three machines. the client making the request will set up a
>connection with the one that answers first, and ignore the
>others. just by the simple voodoo of process scheduling and
>network topology, the load will more or less balance out across
>all three machines.
Not entirely true. This will "pseudo balance" the load. Once
a client has resolved the IP address for the host, it will
continue to use it. And if that machine dies, until the entry
expires from DNS the client will get a host not found error (or
host not responding).
>
>the upside is that the busier a machine happens to be, the less
>likely it is to be the first one that answers. therefore, the
>network tends to balance out its processing load across the
>machines in good Marxist fashion.. from each according to its
>abilities, to each according to its needs.
>
>
>the capacity to duplicate machines also operates with regard to
>the front-end servers. webpage requests are by definition
>independent of each other, so you can have multiple front-end
>machines proxying requests off to the same back-end server.
>
>the minimum configuration for a fairly robust system is to have
>two identical machines at the front passing requests to two
>identical machines at the back. you can put a .45 slug through
>the CPU of any single machine, and the system as a whole will
>continue to operate. by isolating processing to a specific
>group of machines, you can build parallelized subnodes of a
>larger cluster. once you have those, you can tune the
>performance of the subnodes to meet the demands of the cluster
>as a whole.
>
>as you get into other protocols or specialized daemons, you
>introduce more ways for machines to share information, and
>increase the performance or feature set of the cluster. you
>can do quite a lot in a webserver farm with just the three
>pieces i've already mentioned, though. and the good news is
>that you can do it with a stock Apache installation and ordinary
>DNS.
For some more info about Load Balancing, take a look at this
article from Web Techniques:
http://www.webtechniques.com/features/1998/05/engelschall/engelsch
all.shtml
Matt Soffen
==============================================
Boss - "My boss says we need some eunuch programmers."
Dilbert - "I think he means UNIX and I already know UNIX."
Boss - "Well, if the company nurse comes by, tell her I said
never mind."
- Dilbert -
==============================================
____________________________________________________________________
--------------------------------------------------------------------
Join The NEW Web Consultants Association FORUMS and CHAT:
Register Today at: http://just4u.com/forums/
Web Consultants Web Site : http://just4u.com/webconsultants
Give the Gift of Life This Year...
Just4U Stop Smoking Support forum - helping smokers for
over three years-tell a friend: http://just4u.com/forums/
To get 500 Banner Ads for FREE
go to http://www.linkbuddies.com/start.go?id=111261
---------------------------------------------------------------------
