Or, if don't want to spend a dime you can do this with simple cron'ed shell
scripts and scale it your needs. Here's an example with two web servers
192.168.1.1 (primary webserver) and 192.168.1.2 (backup webserver):
1) Configure both servers to your specs. Recompile the kernel on your backup
server to include Network Aliasing/IP Aliasing Support so that you can bind
multiple addresses to a single interface.
2) On the backup server write a cron'ed script to copy (mirror, replicate,
etc..) your chosen files or directories. A really easy way to do this is to
create a .rhosts on the primary server and do something like rsh 192.168.1.1
tar -cf - /dir | tar --atime-preserve --same-owner -xpf - (the - is stdout).
A better and more secure solution would be to use ssh for this. You can get
as elaborate with this as you like and create a checksum and only replicate
when it has changed and so forth.
3) Again on the backup server, possibly even in your replication script, you
can script a ping to the primary web servers IP address. If the ping fails
call the commands to bind the primary web server address to the backup
address using ifconfig:
/sbin/ifconfig eth0:0 192.168.1.1 netmask 255.255.255.0 up
/sbin/route add -host 192.168.1.1 eth0:0
See the NET-3-HOWTO and the IP-Alias mini-HOWTO for more on this.
4) If your primary server fails and the backup has to bind it's address
you'll want to stop the script from binding the address over and over. Maybe
check for the existance of a file in var/local/ that will be either created
or deleted, it's your choice.
There you go free and easy. You can even add second NIC to each machine to
create an internal RFC1918 (private) net similar to what M$ NT uses for
clustering(for just a few dollars, marks, or pesos more). I'd like to take
credit for this but someone else clued me in in a class I took. Bob, if you
watch this list, thanks.
-Chris
On Tuesday, August 03, 1999 4:30 PM, Elliot Poger [SMTP:[EMAIL PROTECTED]]
wrote:
>
>
> flippie wrote:
>
> > By Clustering I mean having 2 machines, that is not dependant on each
other.
> > Lets say the harddrive goes on the one, the other one must take over.
These two
> > machines must not share anything. It must be, as if these two machines
have the
> > same IP address, but still be mirroring between them.
>
> I think the newest version of TurboLinux has something like that. I
haven't tried
> it yet, but I talked to some dude at LinuxWorld about it... (great show,
by the
> way).
>
> Or, if you're willing to spend the dough, you can get a hardware
> load-balancer-failover box like BigIP and put it in front of all the
machines.
>
> -Elliot
>
>
> -
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