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  1. Hadoop Common
  2. HADOOP-1134

Block level CRCs in HDFS



    • New Feature
    • Status: Closed
    • Major
    • Resolution: Fixed
    • None
    • 0.14.0
    • None
    • None


      Currently CRCs are handled at FileSystem level and are transparent to core HDFS. See recent improvement HADOOP-928 ( that can add checksums to a given filesystem ) regd more about it. Though this served us well there a few disadvantages :

      1) This doubles namespace in HDFS ( or other filesystem implementations ). In many cases, it nearly doubles the number of blocks. Taking namenode out of CRCs would nearly double namespace performance both in terms of CPU and memory.

      2) Since CRCs are transparent to HDFS, it can not actively detect corrupted blocks. With block level CRCs, Datanode can periodically verify the checksums and report corruptions to namnode such that name replicas can be created.

      We propose to have CRCs maintained for all HDFS data in much the same way as in GFS. I will update the jira with detailed requirements and design. This will include same guarantees provided by current implementation and will include a upgrade of current data.


        1. BlockCrcFeatureTestPlan.pdf
          19 kB
          Raghu Angadi
        2. BlockLevelCrc-07032007.patch
          168 kB
          Raghu Angadi
        3. BlockLevelCrc-07052007.patch
          178 kB
          Raghu Angadi
        4. BlockLevelCrc-07062007.patch
          177 kB
          Raghu Angadi
        5. BlockLevelCrc-07102007.patch
          186 kB
          Raghu Angadi
        6. BlockLevelCrc-07122007.patch
          193 kB
          Raghu Angadi
        7. DfsBlockCrcDesign.htm
          21 kB
          Raghu Angadi
        8. HADOOP-1134-01.patch
          189 kB
          Raghu Angadi
        9. HADOOP-1134-02.patch
          203 kB
          Raghu Angadi
        10. HADOOP-1134-03.patch
          203 kB
          Raghu Angadi
        11. readBuffer.java
          1.0 kB
          Raghu Angadi

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              rangadi Raghu Angadi
              rangadi Raghu Angadi
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