Coda File System

RE: Coda and webserver mirroring?

From: Jason Pratt <>
Date: Fri, 16 Nov 2001 16:45:38 -0500
i was trying to do the same thing as you, valerio, and had to give up as
well (i was clearly missing something in the

however, the conclusion that i came to was that:

1> both webservers would be file servers (to achieve real-time
2> both webservers would have coda clients pointing to /themselves/.

that way, both servers would automatically mirror each other (with only
one of them serving as the SCM, of course,) but would be fault tolerant,
in the event that one of them (even the SCM,) failed. 

my hopes were raised that this would work after i read about a company
that actually built an LVS web server cluster appliance using this
technique. however, i had to give up on installing coda, as well - i
just couldn't get the clients to mount reliably, the servers to talk to
each other, etc. obviously i was doing something wrong, but i too
noticed that the documentation wasn't completely maintained - it seemed
out of date, and in some cases clearly out of sync with recent releases
(config files in different locations, different formats, etc.)

i think adoption of coda would be *greatly* increased if this one area
were improved. i also appreciate the fact that few people (one person?)
maintain coda, and they seem to be pretty well loaded down. is there any
discussion of the possibility of opening up maintenance of the
documentation (via a coordinated effort with the development team, not
anecdotal advice,) or is there currently a good source of documentation
outside of the site? i didn't find any.

i was (and am still,) curious about performance data when using the
above technique. is there significant overhead or lag when a coda client
accesses a local repository, assuming that the access is 99% read, and
essentially random (as is the case with many web servers, especially in
the asp space.) does this even work?

Jason bond pratt 
lead infrastructure architect 
34405 w twelve mile rd, ste 123 
farmington hills, mi  48331 
p 248.848.1720x122 
f 248.848.1905 

-----Original Message-----
From: Valerio Morettini []
Sent: Friday, November 16, 2001 4:14 PM
To: Jan Harkes
Subject: Coda and webserver mirroring?

> I also believe you've got the whole idea of how the replication works
> wrong.
> The way you've configured it, /usr/www (normally /vicepa) will store a
> directory tree of anonymous file data objects. The server's RVM will
> hold associated metadata and this data and metadata is combined by the
> client and exported through the /coda mountpoint.

Ok, i messed up the whole thing inside my poor head :)

So the only way for doing replication is actually having the webservers
coda clients?
If i've not misunderstood again, this means that  the replication is not
full, but happens only on the data hoarded
by the clients... so if the server goes down and a web user requests a
which had not been hoarded,
the webserver cannot serve it to him...and this is not very good for
websites :(
May i ask you an advice on a possible real-time solution? (no rsync or

Anyway, thanks for the answer, you were way too kind. I deserved to be
flamed really :)

Received on 2001-11-16 16:35:50