index can not Optimize

[David Gao]

the index is created by indexwriter.AddIndexesNoOptimize using lucene.net 2.1
at last it is about 350M,and has about 6000 cfg files
but it can;t be optimized now,the Optimize programe running about 5
hours and the system shows its io read is about 58G,write about 43G
in the index directory, i find that, some files are created(like
*.tis,*.tii,*.frq,*.cfg...),but serverl minutes later it only leaves
two files :segments.gen and write.lock
and then these files created again and again,...
it looks like that the optz is in endless loop..
why??thanks:)

and this is my code

                            reader = IndexReader.Open(spath);
                                IndexWriter indexwriter = null;
                                try
                                {
                                    Directory directory =
FSDirectory.GetDirectory(spath, false);

                                    indexwriter = new
IndexWriter(directory, new StandardAnalyzer(), false);
                                    indexwriter.Optimize();
                                    _log.Info("☆Lucene Make
Optimized." + directory);

                                    directory.Close();
                                }
                                finally
                                {
                                    if (indexwriter != null)
                                    {
                                        indexwriter.Close();
                                    }
                                }