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CurtE Guru
Joined: 17 Apr 2004 Posts: 364 Location: Minneapolis, MN
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Posted: Thu Apr 22, 2004 3:57 am Post subject: I have 2 servers, how can I make them one to the Internet? |
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If my company name is www.mysite.com and someone is trying to access my site, how do I get the Internet to recognize xxx.yyy.zzz.89 and xxx.yyy.zzz.90 as the same site?
If the xxx....89 server goes down, how does xxx....90 take over?
If you ping www.mysite.com, will it find one or both servers?
Be verbose, I'm a little confused. |
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Chris W l33t
Joined: 25 Jun 2002 Posts: 972 Location: Brisbane, Australia
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Posted: Thu Apr 22, 2004 4:52 am Post subject: |
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There are a couple of ways to start down this path: round-robin DNS entries or reverse proxies are the two that immediately spring to mind. I'm sure there many dedicated solutions available.
With round-robin DNS the name www.arbitrarydomain.com is has two or more A entries pointing to different IP addresses. A separate name is also given to each IP address so they may be separately accessed. Reverse entries should point to the shared name. The BIND, or other, DNS server will allocate one or other of the addresses (round-robin or some other method) to name resolution requests as they arrive. Load is effectively spread but this does not provide failover on its own.
The reverse proxy is a machine that accepts connections and either serves them from cache, or goes to an internal server for the content. Combined with a DNS it can cycle through an arbitrary number of backend servers while the end-user only ever sees a single address.
Handling failover can be as simple as removing the dead server from the DNS rotation. The dead address with still be cached on the client side, so this may take a short while to take effect.
Care must be taken with web applications to ensure that state information is available across all web servers because subsequent request may not be directed to the same server.
You should probably also read at http://www.linuxvirtualserver.org/ _________________ Cheers,
Chris W
"Common sense: The collection of prejudices acquired by age 18." -- Einstein |
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