are load balancing and mirroring similar concepts?

Hi all,

This is a very simple question that is confusing me. I'm a bit
confused about whether load balancing and morroring are similar
concepts? I am referring to web server load balancing here. As far as
I understand mirroring is keeping duplicate copies of web pages in
different geographical locations to reduce number of hops whereas load
balancing is redirecting traffic to other servers containing copies of
web pages. So in other words, when load balancing is done, the servers
have to contain same copies of pages (which makes it identical to
mirroring). Am i right?

Please unleash my confusion!
Ben

Ben wrote:

So in other words, when load balancing is done, the servers
> have to contain same copies of pages (which makes it identical to
> mirroring). Am i right?
>
Not necessarilly and not often (correct me if I am wrong). Load balancing is
usually implemented on cluster systems where nodes run their local copies
of web server software but web pages are stored on some shared external
disk array.


--
Sandro Mangovski
<Fish:#linux>@irc.idolnet.org
PGP Key:
QOTD: The justification of profit is profit.

Ben wrote:
> This is a very simple question that is confusing me. I'm a bit
> confused about whether load balancing and morroring are similar
> concepts? I am referring to web server load balancing here. As far as
> I understand mirroring is keeping duplicate copies of web pages in
> different geographical locations to reduce number of hops whereas load
> balancing is redirecting traffic to other servers containing copies of
> web pages. So in other words, when load balancing is done, the servers
> have to contain same copies of pages (which makes it identical to
> mirroring). Am i right?

You already answered most of Your own question.

But, load balancing and mirroring have nothing to do with one-another:

In Your example, You can have copies of specific data stored at
different locations (mirrors). You can then present the user with a list
of available mirrors and let them chose one of them. kernel.org does
exactly this. - Strictly speaking, this is not load-balancing, although
it will eventually balance the load.

Load balancing for itself is a different thing and mostly has to do
with routing (no matter what is being routed, whether it's web pages or
a ssh session): If You have more than one route to any given desti-
nation, You might want to parallelize those routes to get a higher
transfer rate. The thing is that in this context, "load balancing" only
goes for _connections_, not for _services_. So if You spread, say,
http-requests over multiple identical (mirrored) web-servers, this is
not considered load balancing, but rather redundancy.


Cheers, Jack.

--
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