noob question regarding redundancy issues

need ideas -
which db offers distributed redundancy and automatic switching? (when one fails, another automatically takes over. the user will never be affected) does the "auto-switching" require additional hardware or some type of softare resolution? furthermore, what if the "switch" failes? does it need redundancy in it too?

the issue gets deeper~ this db is linked to some sort of java web container or app server. havn't yet decided on one yet. so, should the db be on separate machines, what happens if the web container (app server) dies? is there a webserver that offers distributed redundancy and again, auto switching?

constriants: open-source db or relatively cheap ones.
             application must not go off line, hence the lvl of redundancy we're throwing @ it.

You're going RIGHT Over anyone's heads here; though I'm a lol @ the answers you get.

If I was you, I would ask it on the programming board on this forum:
http://www.mega-tokyo.com/forum/

It's a board for OS hackers; they're pretty hardcore.

i lol @ megatokyotomorrow

Use Tandem mainframes to run the database, connect your Java server with TCP/IP and for each process create a child thread in Java when transfering.

hp nonstop? expensive :(

You want fault tolerance, not redundancy (although it is part of fault tolerance).

>>6
 fault tolerance is built within our software and we can only go as far as the software caters. so if say a hardisk fails, we need the redundancy. but yes, ok, in a more abstract term, we need fault tolerance in our mission critical app.

>>4
does tandem comes with its own java webcontainer? cos i guess even having the box itself, it'll just be stupid expensive to impl our webcontainer on it that utilises that TMR.

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