Fast I/O plugins for Spark
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Crail-Spark-IO contains various I/O accleration plugins for Spark tailored to high-performance network and storage hardware (RDMA, NVMef, etc.). Spark-IO is based on Crail, a fast multi-tiered distributed storage system. Spark-IO currently contains two IO plugins: a shuffle engine and a broadcast module. Both plugins inherit all the benefits of Crail such as very high performance (throughput and latency) and multi-tiering (e.g., DRAM and flash).


  • Spark 2.0.0
  • Java 8
  • RDMA-based network, e.g., Infiniband, iWARP, RoCE. There are two options to run Spark-IO without RDMA networking hardware: (a) use SoftiWARP, (b) us the TCP/DRAM storage tier


Building the source requires Apache Maven and Java version 8 or higher. To build Crail execute the following steps:

  1. Obtain a copy of Crail-Spark-IO from Github
  2. Make sure your local maven repo contains Crail, if not build Crail from Github
  3. Run: mvn -DskipTests install
  4. Add crail-spark-1.0.jar as well as its Crail dependencies to the extra class path in Spark, both for the driver and the executors
spark.driver.extraClassPath     $CRAIL_HOME/jars/*:<path>/spark-io.jar:.
spark.executor.extraClassPath   $CRAIL_HOME/jars/*:<path>/spark-io.jar:.


To configure the crail shuffle plugin included in spark-io add the following line to spark-defaults.conf

    spark.shuffle.manager		org.apache.spark.shuffle.crail.CrailShuffleManager

Since spark version 2.0.0, broadcast is no longer an exchangeable plugin, unfortunately. To use the crail broadcast plugin in Spark it has to be manually added to Spark's BroadcastManager.scala.


For the Crail shuffler to perform best, applications are encouraged to provide an implementation of the CrailShuffleSerializer interface, as well as an implementation of the CrailShuffleSorter interface. Defining its own custom serializer and sorter for the shuffle phase not only allows the application to serialize and sort faster, but allows applications to directly leverage the functionality provided by the Crail input/output streams such as zero-copy or asynchronous operations. Custom serializer and sorter can be specified in spark-defaults.xml. For instance, crail-terasort defines the shuffle serializer and sorter as follows:



PRs are always welcome. Please fork, and make necessary modifications you propose, and let us know.


If you have questions or suggestions, feel free to post at:!forum/zrlio-users

or email: