public static long getWALBlockSize(Configuration conf, FileSystem fs, Path dir)
    throws IOException {
    return getWALBlockSize(conf, fs, dir, false);
  }
Blocksize returned here is 2x the default HDFS blocksize unless explicitly set in
Configuration. Works in tandem with hbase.regionserver.logroll.multiplier. See comment in
AbstractFSWAL in Constructor where we set blocksize and logrollsize for why.
@return Blocksize to use writing WALs.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/WALUtil.java