code: private void initParityConfigs() {
      Set<String> acceptedCodecIds = new HashSet<String>();
      for (String s : conf.get("dfs.f4.accepted.codecs", "rs,xor").split(",")) {
        acceptedCodecIds.add(s);
      }
      for (Codec c : Codec.getCodecs()) {
        if (acceptedCodecIds.contains(c.id)) {
          FSNamesystem.LOG.info("F4: Parity info."
            + " Id: " + c.id
            + " Parity Length: " + c.parityLength
            + " Parity Stripe Length: " + c.stripeLength
            + " Parity directory: " + c.parityDirectory
            + " Parity temp directory: " + c.tmpParityDirectory);
          acceptedCodecs.add(c);
          if (c.stripeLength > this.stripeLen) {
            // Use the max stripe length
            this.stripeLen = c.stripeLength;
          }
        }
      }
      FSNamesystem.LOG.info("F4: Initialized stripe len to: " + this.stripeLen);
    }
docs: This function initializes configuration for the supported parities.
  
  Currently, we support RS and XOR. Those two can have different
  configurations individually. Respective configurations will be used when
  placing the parity files. There is one exception. The stripe length is
  calculated based on the maximum of the stripe lengths of the individual
  parities.