code: public void flushSegmentIndexBuffers() {
          SegmentIndexBuffer sib = null;
          
          while((sib = _sibManager.poll()) != null) {
              File sibFile = getSegmentIndexBufferFile(sib.getSegmentId());
              try {
                  _sibManager.getSegmentIndexBufferIO().write(sib, sibFile);
              } catch (Exception e) {
                  _log.warn("failed to write " + sibFile.getAbsolutePath());
                  sibFile.delete();
              }
          }
      }
docs: Flushes accumulated segment index buffers to disk.