www.columbia.edu Web Site Backup

A www.columbia.edu that always reachable from everywhere

As part of the University's disaster preparedness efforts, key portions of the content of the official University web pages at www.columbia.edu are backed up by Akamai Technologies, Inc. This mirror service supplements our replicated web servers and high reliability file servers.

The primary purpose of the web backup service is to maintain a web presence in the event of a major disaster and to allow the University to communicate via the web with the rest of the world, including our students, faculty and staff and their colleagues, friends and families. However, even a short-term network or web server failure will cause the Akamai mirror to be used.

What's mirrored at Akamai?

The top several levels of the www.columbia.edu tree are automatically copied to Akamai servers in other parts of the country each morning at 5:00 AM. This includes most pages directly reachable from the main web page, including the text (but not audio or video) of the Columbia News page.

In the event of a major incident that requires updates to off-campus copies of the the web pages, AcIS staff will work with other University officials to update the content on the Akamai servers. We are also working on a related project to develop an emergency web bulletin board system to enable limited two-way communication when email systems are unavailable.

What's not mirrored at Akamai?

A significant amount of the University web content is not copied to Akamai; the service is expensive and our use of it is meant only to protect highly time-critical information that requires widespread, reliable dissemination. Furthermore, only static content can be mirrored.

Specifically, the following types of content and web sites are not mirrored:

Web sites that are not hosted on the central AcIS web servers. These include a number of school and departmental sites that have been outsourced or are run by the school, department, or other unit. (If you would like your web site hosted by AcIS, please contact [email protected].)
Dynamically-generated content such as search pages (including pages such as AcIS News which are generated dynamically using a search engine behind the scenes).
Web-based applications such as AcIS Computer Account Management. These applications are dynamic, and require back-end application servers, databases and so on that can not be mirrored at Akamai.
Web pages and applications not run on AcIS servers such as Student Services On-line.
Any secure web pages on the AcIS-run secure web servers (HTTPS).

How do I know if my files are mirrored?

The mirror server is named www-fail.cc.columbia.edu. Point your browser there to test it. Please note that during normal operation, any pages you author that link explicitly to http://www.columbia.edu instead of using a relative URL will go back to the AcIS web server and will not be a proper test. When the main server is considered down by Akamai, these links will also be redirected to the fail-over server at Akamai. To test these links, either make them relative URLs in your web pages or explicitly test them by hand on the fail-over server. To make a relative URL use, for example, <A HREF="/cu/dept/sample.html"> instead of <A HREF="http://www.columbia.edu/cu/dept/sample.html">.)

Why am I connected to Akamai when I can still reach Columbia?

The Akamai fail-over service works automatically and can be triggered by even relatively minor short-duration Internet connectivity outages. See "How it works", below.

You can tell your browser is on the backup server because Akamai's server sends you a redirect to www-fail.cc.columbia.edu. This appears in the URL text box. This is actually not the optimal way for this to work since references to relative URL's will also stick on the fail-over server.

To get "un-stuck" you need to re-reference www.columbia.edu and may need to restart your browser. This is because the IP address of www.columbia.edu that points at the fail-over server is cached by some browsers. This is a bug in the browser and/or operating system but it's not like we have much influence over Microsoft to fix this for deployed browsers!

How does my organization add pages to the mirror?

If you have critical pages that are not currently being copied to the fail-over mirror, please contact [email protected].

How it works

The Akamai service consists of two parts: Firstpoint and Edgesuite. Firstpoint checks our primary web server every few seconds from about a dozen locations around the Internet and uses the results to determine when the web server is not reachable. The domain name, www.columbia.edu, is actually served by DNS servers run by Akamai, not Columbia. When Firstpoint determines that our web server is not reachable, it tells the Akamai DNS system to return the IP address of the fail-over server(s) at Akamai data centers, rather than the IP address of our server at Columbia's computer center.

At this point, Edgesuite is used. The IP address returned by Firstpoint goes to an Akamai web server which in turn generates a redirect to www-fail.cc.columbia.edu which is actually a pointer into Akamai's Edgesuite web service. [The extra step of referring into Akamai's Edgesuite is a recognized problem and is why the name "www-fail.cc.columbia.edu" shows up during a fail-over. Normally, Akamai's Firstpoint service is used by large corporations that have two or more of their own data centers to fail-over to. We are using Akamai's Edgesuite data centers as the fail-over site.]