private File getFileLogSegment(ReplicaId replica) {
    return Paths.get(replica.getReplicaPath(), LogSegmentName.fromPositionAndGeneration(0, 0).toFilename()).toFile();
  }
Creates {@code fileCount} files and {@code dirCount} directories at {@code dir}.
@param dir the directory to create the files and dirs at
@param fileCount the number of files to be created
@param dirCount the number of directories to be created
@return the list of files,dirs created as a pair.
@throws IOException
ambry-store/src/test/java/com/github/ambry/store/StorageManagerTest.java