fault tolerant web servers on freebsd

[Maciej Jan Broniarz]

W dniu 10-04-05 22:08, Tonix (Antonio Nati) pisze:
> Maciej Jan Broniarz ha scritto:
>> W dniu 10-04-05 17:45, Mike Jakubik pisze:
 >
> Just to use exact words, fault toulerancy is not possible with any
> FreeBSD/Linux O.S.
> F.T. means outage can occur in every moment, but all current operation
> will be always completed by other equipments; so there will not be
> interrupted/lost operations.

Hmm. Thanks for the tip. Which *NIX os can be used to build an FT 
solution then? Solaris? AIX? HP-UX?

> Carp is fine for HA is you have always both db and file storage always
> available.
> For DB you can use MySQL replica, cross-replicating local MySQL data
> among all servers. Each server will keep its own copy, always up to date
> with other servers.
> This will make all DB data always available, except data recorded in the
> last milliseconds.
>
> About file storage, you must have an external reliable NFS server.

So, to be redundant one should run 2 x web servers + 2 x storage +2 x 
mysql. Sounds like fun, but also like a lot of work. So how do the web 
hosting prividers manage to use FreeBSD for theirs solution?
I am curious do they have a cluster/reudndant solution for every part of 
the system, or they just accept thet something will fail at some time.

Best regards,
mjb