Path createStoreDir(final String familyName) throws IOException {
    Path storeDir = getStoreDir(familyName);
    if (!fs.exists(storeDir) && !createDir(storeDir))
      throw new IOException("Failed creating " + storeDir);
    return storeDir;
  }
Create the store directory for the specified family name
@param familyName Column Family Name
@return {@link Path} to the directory of the specified family
@throws IOException if the directory creation fails.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegionFileSystem.java