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Spark is can be used with a variety of data formats such as Hadoop SequenceFiles, which resemble Avro files in many ways; but Avro can be used outside of Spark, whereas SequenceFiles are less easy to work with outside of their intended Hadoop or Spark context. With Avro, it's more feasible to write the kinds of utilities that we need to support our system, which might do things like package packaging up directories of flat files into Avro files, or perform performing analytical or diagnostic functions.
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