Coda File System

Re: Coda Server Access Optimizations

From: Brian White <>
Date: Fri, 28 Feb 2003 10:19:31 -0500
> > All the client/servers at site X (servers A, B, and C) can communicate over
> > fast ethernet, as can the client/servers at site Y (servers D and E) but
> > there is only a slow link between the two sites.
> >
> > When a client on site Y changes a file, does it try to
> >
> > a) push that change to all five servers
> If the 'observed' bandwidth of the link to the servers A,B, and C is
> above the weak-connected threshold (about 64kB/s) the Coda client pushes
> updates to all servers.

If there are many sites, does only one have to be belowe the threshold
before it goes to the single-push/server resolution method?

> > b) push that change to both local servers (D and E) and let them deal with
> >    propogating to the other site
> > c) push that change to the closest server and let it deal with propogating
> >    it to all the other servers
> If the available bandwidth is insufficient, Coda stores writes locally
> and in the background reintegrates with a single server, although it
> typically tries to send updates to the server that appears to have the
> best connectivity. When the reintegration completes, the client triggers
> server-server resolution which propagates the update to all other
> servers.
> So in reality you are probably worse off by letting the servers resolve
> over the slow link because the data is shuttled back and forth several
> times.
> Typically servers that share the responsibility for a volume are located
> at the same location. In your case you would either have 2 volume
> storage groups, with some volumes on A/B/C and others on D/E. Clients at
> site Y would typically be weakly connected to A/B/C and have strong
> connectivity to D/E.

What I'm trying to accomplish is a "shared drive" that is common across the
entire company, including offices in other cities connected only through a
VPN over the public internet.  NFS is slow and rsync works well only in
one direction as it cannot resolve conflicts.

Ideally, someone from here can take their laptop to another office, plug
it in to the wall, and not be able to tell much of a difference from their
home site.  NIS and some clever DHCP/DNS takes care of the networking
aspects; now I need to solve the filesystem difficulties.

                                 ( )

          I don't suffer from insanity... I enjoy every minute of it.
Received on 2003-02-28 10:23:19