One index for two locations

Hi,

my main root directory (Apache web server) is /www/docroot
and the url is http://servername/

Also I have configured alias http://servername/archive with
physical location /ext/archive

Is there any way I can build one search index for two directories
i.e. /www/docroot and /ext/archive

Or probably the other solution will be to build two separate indexes
and somehow tell namazu.cgi to search both of them.

Sorry if this has been discussed already but I couldn't find an answer.

Thanks
Peter