There are several parameters in the solrconfig.xml that can be used to tune your solr server. Our solrconfig.xml is designed to ship a reasonable configuration for the most standard use cases.
For use cases with very large indexes or high performance requirements it makes sence to tune those parameters
This value is "true" by default in our configuration. By setting this value to true solr only writes one file for indexes instead of many. This is a little bit slower but more robust to prevent errors with "Too many open files".