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当我们从 HDFS 文件中读取一个字节时,这是否意味着从集群中某处的磁盘读取了一个完整的 HDFS 块(假设不涉及缓存)?
答案是不。
这受参数影响(可能不是排他性的)dfs.datanode.readahead.bytes,默认为4MBhadoopv2.2.0
dfs.datanode.readahead.bytes
4MB
v2.2.0