Re: backup web server
On Mon, 28 Feb 2005 08:54:29 -0800, Eric Gaumer
<gaumerel@ecs.fullerton.edu> wrote:
> Kevin Coyner wrote:
> > I have a client whom I host on my server that insists on virtually 100%
> > uptime for his website. While 100% might be stretching it a bit, how is
> > this best done? Is it a combination of software and DNS?
If the website doesn't include databases the setup is easier.
> > I know some sites run mirrors, but that usually involves clicking a link
> > to go to that specific mirror. Is it possible to have this be
> > transparent, so that if person visiting the site fails to connect to the
> > primary webserver (because it is down), then he/she is automatically
> > switched to a backup mirror?
> >
> > I actually have two separate boxes with different IP's, both running
> > Debian and Apache 1.3. The client's website is on one box and the other
> > box could be used if needed.
> You need to do load balancing. Typically you use an appliance (we use Cisco Local Director)
> but you could build a load balancer using iptables.
For a cheap load balancer you could also use the Linux Virtual Server.
It's rather easy to configure using Keepalived.
http://www.keepalived.org/
> Basically one box (the load balancer) answers incoming requests and hands them off to a pool
> of servers that all share the content. If one goes down then the director does not send it
> requests (it is said to be offline).
Keepalived allows the setup of a spare load balancer that would
take over when the main load balancer fails.
> If the local director goes down you loose the cluster. This has only happened once in five
> years. Our network sees roughly 500 million hits a day and we do a sustained 1.2Gbps of
> traffic at any given time.
The cheapest solution you can do is use heartbeat. If you can allow for a
10 second downtime (it's configurable). It will take the IP of the web
server once it fails.
This could give you and idea of what can be done (without the NFS stuff,
maybe you can use rsync... I dont't know...)
http://www-128.ibm.com/developerworks/linux/library/l-halinux/
Regards,
Nelson.-
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