Coda File System

Re: Files Bigger Than Cache Size

From: <>
Date: Thu, 31 Jan 2008 08:46:12 +0100
Hi Gordan,

On Wed, Jan 30, 2008 at 12:18:43PM +0000, wrote:
> Right. So to handle 2GB files, the RVM log would also need to be 2GB? I 

No. There are "cache size", "RVM size" and "rvm LOG size". The last one
is the least to be concerned about.

Asking Google for "rvm log size", the second entry looks as follows:
Optimizing Coda 6.x - Codawiki
A log size of 20M should work for any setup; Note that the size of the RVM is dependent on the number of files and directories across all volumes (not per ... - 19k

The "Client cache" section on that page needs improvement though. There
are contradicting statements, each of those would be misleading if taken

> noticed that 8GB cache works fine, but at 16GB (on 32-bit x86) venus seems 
> to fail to initialize.

Max usable RVM size is about 1GB. This is mentioned on the Wiki.
Jan points out that bigger sizes are possible but in reality they are
not to be recommended, in any case not for a casual user or novice admin.

(The above concerns 32-bit systems, may be considerably different
on 64-bits systems, then it is you who provides the answers by experimenting :)

When you ask Venus for a certain cache size, it guesses how many files
and modification entries you might need (unless you specify explicitly)
and allocates RVM accordingly.
This may lead to allocation of a potentially huge RVM - which possibly fails.

A huge RVM, when it is populated, makes Venus memory footprint very large,
affecting the performance of the client host.

So, if you will be accessing primarily big files, always specify
explicit (low) file / cml numbers when setting up a client.

> >1. Coda does not handle files over 2G in size.
> >2. A Coda client reads the whole file into the cache at open() so unless
> >you have a _really_ fast network you do not usually want to wait as long.
> Not exactly a big problem in the day and age of gigabit ethernet. :-)

Coda is designed as a global file system with emphasis on resilience
against network and server failures, not on LAN peformance.
Coda LAN performance is quite reasonable, but do not take for granted that you
fill a gigabit line with a single transfer.
Otherwise, it is latency which matters, not the bandwidth.

Received on 2008-01-31 02:51:34