The SVN Apache server was not happy trying to read from /cvs/cds/caltech/svn/; it complains "Value too large for defined data type" when trying to modify certain files.
To remedy this, Eric ran an rsync job to copy over the svn directory to /export/home/svn/, which is directly on nodus rather than on the NFS mount.
Accordingly, I edited the httpd-ssl.conf file in /cvs/cds/caltech/apache/etc/ so that SVNPath points to /export/home/svn. The original config file is preserved as httpd-ssl.conf.old_20140609.
Then I started the Apache server using the instructions on the 40 m wiki (search "Apache"). The SVN now appears to be working fine; you can svn up and svn ci as necessary.
However, this means that we now need to start backing up /export/home/svn/, rather than the NFS-mounted directory.