(Illustration by Gaich Muramatsu)
On Wed, Jul 18, 2001 at 08:30:47AM +0200, Michael Radzewitz wrote: > The coda-server is able to do > this but it needs one SCM to control all actions. Is there a way of setup > more than one SCM so that the second or third one will take over the control > if the first one fails? Ok, big misunderstanding here. Yes, we do have a SCM (System Control Machine). However, it does _not_ control all actions. The only way the SCM is different is because the user and volume databases are using a very simplistic replication mechanism. They are only written to on the SCM and then copied over to all other servers. As a result, the SCM is only needed during volume creation and destruction, and when users are added/removed/updated. During regular day-to-day operation the SCM is just another server. Any server can provide a client with volume location information, all servers independently service requests for the volume replicas that are stored on them. All servers have the same information available as the SCM and essentially have the same capabilities. If the SCM is missing, new volumes cannot be created, and in case the SCM is truely dead the only thing that has to be changed is to tell all clients who will become the new SCM. That way they know who to query for updated databases. # echo new_scm_server_name >> /vice/db/scm # /etc/rc.d/init.d/update.init restart Now on to the rest. > i am looking for a filesystem which is able to synchronize some files among > some different servers. I think but i am not sure if the coda-file-system > will do this in my situation. This should probably become an entry in the FAQ, preferably annotated with links and people's experiences with the various methods. Right now it is most likely a bit biased, because I'm writing this down ;) Jan Ways of having the same files accessible on multiple machines, one way mirroring, rsync - Only syncs at intervals (when using the cron). omirr - Kernel patch + daemon that updates the slave. CVSup - Works well with CVS archives but can handle anything. true-sync tools Unison - Heuristically derives a log of changes from observing the differences between 2 clients. Then exchanges these logs, no server involved. central repository CVS - Have to explicitly check-in/out updates. Keeps a full history, so it is possibly to roll-back to an earlier snapshot. network filesystem NFS, Samba - Without the server, all access is lost. distributed filesystem AFS - Read-only replication. Coda distributed file system - 'Write many, read one' replication and disconnected operation. Intermezzo - Keeps a log of changes at kernel level, ships logs to the server and receives update logs. Also handles disconnected operation. Rumor replicated file system - Optimistic peer-to-peer replication, no server involved.Received on 2001-07-18 08:11:36