log.debug("Write " + length + " took " + ( System.currentTimeMillis() - start ));
    }


    static final void randBytes ( Random r, byte[] buffer ) {
        // regular nextBytes is not reproducible if the reads are not aligned
        for ( int i = 0; i < buffer.length; i++ ) {
            buffer[ i ] = (byte) r.nextInt(256);
        }

    }