On 22/07/2004 11:14 AM +1000, Mary Gardiner wrote:
On Thu, Jul 22, 2004, Trevor Tregoweth wrote:Hi All
after my last post, which i think wasn't quite to the point, i would like to find out how to have a web-backup server, and how to configure them, so that when one goes down the other takes affect.
Thanks for you help and suggestions
[..snip..]
FWIW, I've setup a high availability/load balancing cluster using TurboLinux (which uses LVS). The way I did it was to have a 3rd server that had all the static content on it. If any changes were to be made to the web content, it would be done on this 3rd server. Whenever the user logged out of FTP, it would run rsync to copy the web content onto the front end web servers. If anyone tried to FTP to any of the front end web servers, it would forward the connection to the 3rd server.
I guess the only problem with this setup is the single point of failure on the 3rd server, but since it's only holding content, if it goes down it simply means changes can't be made to the web content but at least the web servers can still answer requests on the content they already have.
If you're using sessions and/or SSL, remember to maintain the connection to whichever front end server they connect to, OR ensure you share the session files across the web servers (we used file-based sessions and shared the directory over NFS for this).
All in all, it worked reasonably well. Further to a high availability web server, if you also want to have mail on load balancing, it gets tricky unless you split users over multiple servers, and have a LDAP database or something that tells it which mail server the user is on. I found a program back when I was involved in this project that allowed you to connect to this IMAP/POP proxy daemon and it used LDAP to determine what server the user is on, and connected the client to it.
Anyway, hope this helps.
Regards, Gonzalo -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
