@Override
    public synchronized void write(byte[] buf, int offset, int length) throws IOException {
      LOG.info("faulty stream write at pos " + getPos());
      injectFault();
      super.write(buf, offset, length);
    }
Faulty file system that will fail if you write past its fault position the FIRST TIME only;
thereafter it will succeed. Used by {@link TestHRegion} too.
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestHStore.java