Coda File System

Re: Extreme Newbie questions

From: Jan Harkes <>
Date: Wed, 27 Dec 2000 13:17:02 -0500
On Fri, Dec 22, 2000 at 01:29:39PM -0600, Kelly Corbin wrote:
> I'm new to the list and wanted to ask some questions about Coda to gauge 
> peoples personal experiences with it.
> 1.  How stable is it?  Do you have problems with data corruption at all?

I still consider Coda in an experimental state. Data corruption hasn't
occured yet, but although we try to avoid it at all cost dataloss is
sometimes possible, especially when a new user is confronted with
server-server or reintegration conflict.

> 2.  What about other DFSs?  Has anyone used anything else and how does 
> it compare to Coda.

Here is a limited comparison.

			NFS		AFS		Coda
reliability		stable		stable		experimental
scalability*1		low		high		medium/high
locally cached files	no		yes		yes
server replication   	none		read-only	read-write
disconnected operation	none		read-only?	read-write

*1 in terms of number of clients per server.

Compared with local disk access, most network filesystems are slower,
access speed depends on network connectivity, server load and other
factors. Coda is relatively slow when doing connected create/remove
operations because of the userspace implementation of the cache-manager
(minimally 2 context switches per request), and the transaction based
metadata updates on the servers, which is great for recovery after a
crash, but limits the number of requests that a server can handle per

> 3.  Is Coda what I'm looking for?  I'm trying to replicate data on web 
> servers but I need 100% data integrity.  Is another application (maybe 
> other than a DFS) better suited for this?

Have you considered using the local disk in conjunction with a mirroring
tool such as rsync? What it that `data', if it consists of database
files, use a replicated database, not a filesystem. When it is mostly
read-only html pages or images, Coda would work (our website is running
like that). When not too many updates are made to the pages, the
local disk + mirroring is probably a lot more efficient.

> 4.  How does Coda run on Linux?  I know it has been supported in the 
> kernel for quite some time, but does it run better on other OSs?

Basically all of the UNIX ports are equally stable as far as the
userspace cachemanager is concerned. They all have different kernel
implementation, so there are probably minor differences in that area.

Received on 2000-12-27 13:17:11