Spreading repository across disks

[jce]

I have a cvs repository on Ubuntu 8 that is being accessed by about 30
clients using ssh.
The repository is on a 200 GB disk "disk1"
There are several projects in the repository.  In one project "Data",
each user has a subdirectory.
So there is Data/Sam, Data/Adam, Data/Mark, etc.

One user, Sam, has gotten up to 138 GB.
I want to move the subdirectory to another disk so i can free up space
on sda

 i tried

cd /cvsroot/Data
rsync -av Sam /mnt/disk2
mv Sam Sam.old
ln -s /mnt/disk2/Sam

Then i ssh'ed to another machine that had the project already checked
out and did:
cd /workingData/
cvs up -d Sam
>Nothing known about Sam.

can someone help?
what's the right way to move the contents of a directory in the
repository to another disc, without impacting endusers?