Coda File System

Re: High availability with Coda

From: Jan Harkes <>
Date: Thu, 24 Jun 1999 09:56:46 -0400
On Thu, Jun 24, 1999 at 02:55:22PM +0200, Iniaki Fernandez Villanueva wrote:
> On Wed, 23 Jun 1999, LEE, Yui-wah (Clement) wrote:
> > > We also need to offer this service to linux clients and WinXX clients, but
> > > actually coda client supports only linux.  Because of this we consider these
> > > 2 nodes like coda clients and mounting all files under its own /Coda
> > > directory. Afterwards we exports these two directories with Samba and we
> > > obtein a simple file system server with any client (Linux,Win9x,WinNT,..).
> > 
> > Coda already supports Win9x (alpha releases), it also supports FreeBSD
> > as well as NetBSD.  So you probably do not need to re-export Coda via
> > Samba.
> Yes, but I would like a transparent service to the client, so ANY client 
> could connect to my Coda-server without Coda source. Any idea?
> Thanks 
> 	Iniaki

Hi Iniaki.

It is possible to export the filesystem from a Coda client using Samba
or NFS. For Samba it just works, the NFS daemon doesn't like to export
other network filesystems, and therefore needs to be started with the
--re-export flag (this is at least for the userspace nfsd, haven't tried
the knfsd).

You do need to give users a way of obtaining a Coda authentication
tokens, logging into the Coda client machine and running clog. Also
conflicts, which can happen during weak/disconnected operation, can only
be repaired on the machine running the Coda client.

btw. Even if you are on a 100Base-T fully connected network, you can
observe weak connectivity if f.i. the server gets overloaded. Also if a
token expires the volumes that user is writing to will start logging his
operations (become disconnected), until he re-authenticates. Ofcourse
that user won't see/realize that he has become disconnected.

I would say that re-exporting Coda through NFS or Samba definitely does
not solve you High Availability problem. First of all the node that
re-exports the Coda-FS will be your single point of failure. And second,
you increase the chances on getting conflicts that will affect everybody
and not just the user causing the conflict. Normally, only the less
frequently occuring server-server conflicts will be visible for all
clients, and most of these are already automatically resolved by the
Coda servers.

Providing only read-only access through the samba/nfs exports can be
done reliably, but that is probably not what you want.

Received on 1999-06-24 10:06:11