18/03/10

Replication
  - a policy for duplicating resources on multiple servers		
  - advantages
    - improve perf. by balancing load
    - improve robustness

Mirroring
  - multiple sites, each with onw copy and separate URLs
  - non-transparent to user
  - doesn't balance load
  - requires separate URLs

Transparent replication
  - client uses a single hostname when requesting a resource,
    regardless of the physical machine that ends up serving
    the content

  A) Round-robin DNS
      The local DNS server chooses one of the IP addressess
      of the backend servers

  B) Load balancing switch

  C) Use a reverse proxy

Content Delivery Networks (CDNs)
  - companies like Akamai place shared reverse proxies at
    strategic locations
  - other medium-sized companies pay Akamai 
  - requests to the Web sites of these other companies are
    directed (by DNS) to the nearest Akamai reverse proxy;
    it handles the request from its cache, if it can;
    else it passes the request on to the original company's
    origin server(s)
  - this gives medium-sized companies access to a global
    network of reverse proxies.



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Class test

mod_mime
mod_dir
mod_alias
mod_negotiation

Listen
ServerRoot
ServerName
DocumentRoot
VirtualHost
DirectoryIndex
ErrorDocument
Alias
Redirect
AddHandler