Coda File System

Maximum volume size (was: Some questions...)

From: Derek Simkowiak <>
Date: Tue, 24 Sep 2002 13:49:41 -0700 (PDT)
> trying to answer some questions based on my own experience, your mileage
> may vary.

	Thank you for your help.

> I run a server with 4G and another one with about 10G, for a long time.

	Excellent!  Just the real-world proof I was looking for.  I wish
this stuff were documented somewhere, as it is on the OpenAFS site

> Unfortunately, you can not count with having more than about 1G RVM per
> one server process.

	First, can you substantiate your claim about the 1 Gig RVM limit?
I just need something harder than "some guy on the mailing list said so".
I'd like to know how you discovered this limitation, and how long ago that
was.  (And, are you involved in CODA source code development?)

	Okay... if the RVM metadata is limited to one Gig (and that RVM
metadata is about 4% of the total volume size), then that means that the
upper limit for a CODA volume is:

(.04)x = 1 Gig
     x = 25 Gig

	25 Gig is then the maximum CODA volume size, due to this 1 Gig RVM
metadata size limit.  Can anyone substantiate this hypothesis?

	Furthermore, does all of the RVM metadata reside in memory at one
time?  If so, my particular RVM metadata will need to be far less than 1
Gig, as I also need room for the other server software that will be

> RVM for the Coda server is on the Coda server that shouldn't be the
> same as your Web servers.

	I think you missed something... Each node in the cluster will be a
webserver and a "backup" CODA server.  Each node in the cluster will also
a CODA client, so that the webserver software has access to the CODA
filesystem.  This will not be a three-tier architecture as described at

	Functionally, it will still be three tier.  But physically, each
node will perform the roles of all three tiers.  Each node will have (a)
strict firewall rules, (b) LVS director load balancer software (ready to
act as a backup if the primary director fails), (c) application server
software (Apache et. al.), and (d) distributed filesystem (using CODA, I
hope).  Each node will be homogenous, in that, when one fails, any other
node can fulfil its duties without interruption to the client.

	In short, I'm trying to use CODA as a low-cost alternative to a
SAN.  And in my opinion, this will be one of the largest markets for the
CODA software, as nothing else is really available for this (very common!)

	Any substantiation on that 25 Gig limit would be greatly
appreciated.  Also, I need to know if all the RVM metadata is stored in

Thank You,
Received on 2002-09-24 16:49:36