(Illustration by Gaich Muramatsu)
On Wed, Sep 22, 1999 at 02:32:50PM +0200, Antoine Brenner wrote: > > Hi, > > I understand that the Read-Write Replicated Volumes can be used to provide > high data availability in case of failure of a server. > But I could see nowhere what happens if the cell SCM server fails. The only way in which the SCM is special, is that it is the server where all others are fetching updated volume location and user databases from. So the SCM is only special in the cases where new users/volumes are added. And by replacing the name of the SCM in /vice/db/scm, and restarting the update daemons on all servers it is possible to switch to a completely different SCM. As all servers have their own local copy of the volume location and user databases, no server relies on the SCM during normal operation, and clients can authenticate and find volumes in the cell by asking _any_ available server. Point a client to a single server in the cell, and it will be able to find all others. > Are the replicated volumes still shared ? I don't understand that question. Shared with what? Replication in coda works as follows: - When a client writes to a replicated volume the update is sent to all accessible servers in the replication group. - When a file's attributes are fetched, the version vectors from all accessible replica's are collected and compared. If there is a difference, some server has missed updates, and a server-server resolution is triggered. - The file is fetched from any of the available replicas. JanReceived on 1999-09-22 12:32:14