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  1. Hadoop Common
  2. HADOOP-11867

FS API: Add a high-performance vectored Read to FSDataInputStream API

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      The most significant way to read from a filesystem in an efficient way is to let the FileSystem implementation handle the seek behaviour underneath the API to be the most efficient as possible.

      A better approach to the seek problem is to provide a sequence of read locations as part of a single call, while letting the system schedule/plan the reads ahead of time.

      This is exceedingly useful for seek-heavy readers on HDFS, since this allows for potentially optimizing away the seek-gaps within the FSDataInputStream implementation.

      For seek+read systems with even more latency than locally-attached disks, something like a readFully(long[] offsets, ByteBuffer[] chunks) would take of the seeks internally while reading chunk.remaining() bytes into each chunk (which may be {{slice()}}ed off a bigger buffer).

      The base implementation can stub in this as a sequence of seeks + read() into ByteBuffers, without forcing each FS implementation to override this in any way.

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              • Assignee:
                omalley Owen O'Malley
                Reporter:
                gopalv Gopal Vijayaraghavan
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