multiple solr instances using same index files?

[Ryan McKinley]

Is it possible / is it an ok idea to have multiple solr instances 
running on the same machine pointing to the same index files?

Essentially, I have two distinct needs - in some cases i need a commit 
immediately after indexing one document, but most of the time it is fine 
to wait 10 mins for changes if that has better performance.

Alternatively i could rsync the index and use the standard distribution 
stuff.  If thats avoidable, it is one less thing...

thanks
ryan