Hi,

I'm trying to create a 100% availability webserver.
I want to do this by having two (or more) servers on seperate networks.

There are two ways i've thought of doing it.

Having two seperate servers which sync each other when something is changed:
Q. How do i tell it to sync everytime a file is changed on the server. I know i can do this with rsync every X minutes- but it MUST be instant.

Using 4 servers- 2 webservers, and 2 fileservers
2 Webservers, MySQL servers with no "data" on, and 2 file servers
Q. Would mounting the fileservers as the /home directory be a good idea? How would I mount both as mirrors? i.e. how would i get both fileservers to be "/home"- that way the will both be editted when a change is made to files.
Q. What about mysql- thats not stored in /home is it?

What are your thoughts.

I'm currently a webhost, and i want to pioneer 100% uptime hosting.

For obvious reasons, there's no such thing as 100% uptime. But you can get close with redundant systems. You could use some sort of cluster filesystem, I would think, like OCFS (from Oracle) or similar. Also, NBD (network block device) along with device-mapping might be able to allow GPFS to be used on multiple servers as a mirror.

I was looking at CODA file system.
The most important thing that needs to be remember is my customer must not have to change anything.
For the customer, I want to be able for them just to be able to upload their files, and forget about it. They must not need to configure anything to work- the server must handle it all.
I was also thinking about other things. I can do /home directory no problem, but what about BIND config files- and the rest of the /etc file- i surely can't network mount this, or the machine won't be able to boot will it?
Would it be best to rsync my config files every 10 minutes or something?

Theres a lot to read of CODA, and the answer would be in there somewhere, but does anyone know if it is possible to have one CODA on the hard drive? And then the other mirrored CODA (still the /home partition) to be at a remote location?

Do you think that if i did it like this it would need any special configuration with things like Apache, Exim etc. I was hoping since that the server has virtual hard drives, it would treat them as normal, and no complex configuration in software would needed.

Also, bandwidth. How much slower will this method be over a hard drive. I can get a 100Mb connection. Would the CODA remote hard drive only need to updated, not read. That would save hard drive.

Also- mysql, would I just have another mysql server acting as a mirror. I know mysql can do this itself, not that i've looked into it much.