Hi, @allen_chu Your jstack shows many DataXceiver threads stuck in epollWait, meaning the DataNode is waiting on slow or stalled client/network I/O. Over time, this exhausts threads and makes the DataNode unresponsive. Please check network health and identify if certain clients (e.g., 172.18.x.x) are holding connections open. Review these configs in hdfs-site.xml: dfs.datanode.max.transfer.threads, dfs.datanode.socket.read.timeout, and dfs.datanode.socket.write.timeout to ensure proper limits and timeouts. Increasing max threads or lowering timeouts often helps. Also monitor for stuck jobs on the client side.
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