fault tolerant web servers on freebsd

[Tonix (Antonio Nati)]

Maciej Jan Broniarz ha scritto:
> W dniu 10-04-05 17:45, Mike Jakubik pisze:
>> You may want to check out carp(4).
>>
>> http://www.freebsd.org/cgi/man.cgi?query=carp
>>
>
> Thanks. Carp is fine, but I still have to figure out how to 
> synchronize data on disks or in the database.  Usign just carp would 
> leave me with two separate databases containing only parts of users 
> input. Is there a soulution similar to drbd+heartbeat on Linux? 
> Geom_gate looks nice, but I have no idea if it has been used in a 
> production enviroment.

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.

The most you can have is HA (High Availability), that means operations 
currently executed on servers which have outage are interrupted, but new 
operations will be completed as they will be executed on other equipments.

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.

Tonino

> All best,
> mjb
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