UnderReplicatedBlocks处理流程

原创
2019/09/01 13:04
阅读数 5K

hdfs处理block副本不足、分布不合理的流程如下:

UnderReplicatedBlocks处理流程图

 

优先级解释:

  • QUEUE_HIGHEST_PRIORITY: the blocks that must be replicated first. That is blocks with only one copy, or blocks with zero live copies but a copy in a node being decommissioned. These blocks are at risk of loss if the disk or server on which they remain fails.
  • QUEUE_VERY_UNDER_REPLICATED: blocks that are very under-replicated compared to their expected values. Currently that means the ratio of the ratio of actual:expected means that there is less than 1:3.These blocks may not be at risk, but they are clearly considered "important". 
  • QUEUE_UNDER_REPLICATED: blocks that are also under replicated, and the ratio of actual:expected is good enough that they do not need to go into the QUEUE_VERY_UNDER_REPLICATED queue.
  • QUEUE_REPLICAS_BADLY_DISTRIBUTED: there are as least as many copies of a block as required, but the blocks are not adequately distributed. Loss of a rack/switch could take all copies off-line.
  • QUEUE_WITH_CORRUPT_BLOCKS This is for blocks that are corrupt and for which there are no-non-corrupt copies (currently) available. The policy here is to keep those corrupt blocks replicated, but give blocks that are not corrupt higher priority.
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