Cassandra丢失节点 [英] Cassandra loss of a node
问题描述
我试图弄清楚如何为两个节点群集设置参数，以便获得精确的副本，如果其中一个节点已关闭...
使用此工具进行检查： http://www.ecyrd.com/cassandracalculator/
I'm trying to figure out, how to parameter my 2 nodes cluster, in order to have an exact replica, if one of them is down... using this tools to check it out : http://www.ecyrd.com/cassandracalculator/
对于以下参数：
Cluster size: 2 / Replication Factor: 2 / Write Level: All / Read Level: One
它给了我结果：
- 您的读取结果一致
- 您可以在丢失无节点的情况下幸免。
- 您实际上每次都是从 1个节点进行读取。
- 您实际上每次都在写入 2个节点。
- 每个节点持有 100％您的数据。
- Your reads are consistent
- You can survive the loss of no nodes.
- You are really reading from 1 node every time.
- You are really writing to 2 nodes every time.
- Each node holds 100% of your data.
除了一个您可以在没有节点丢失的情况下生存之外，我同意所有这些结果。
我不明白为什么群集无法从一个节点丢失中幸存下来，如果一个节点死亡， Write：ALL将写入仅剩下的一个节点，不是吗？
然后，当我恢复第二个节点时，它应该与第一个节点同步，并再次接受写入，不是吗？
I agree with all those result except one, "You can survive the loss of no nodes". I don't get why the cluster can't survive from one node loss, if one dies, the "Write: ALL" will write to the only one node left, doesn't it ? Then when I bring back up the second node, it should synchronize with the 1st, and accept writes again, doesn't it ?
如果错误，有人可以向我解释原因吗？
If I'm wrong, can someone explain to me why ?
编辑：
更多配置会给我相同的结果，除了持有百分比：
More Configuration will give me the same results except for the holding %:
Cluster size: 3 / Replication Factor: 2 / Write Level: All / Read Level: One
Cluster size: 3 / Replication Factor: 2 / Write Level: Quorum / Read Level: One
即使我尝试与读取而不是写入保持一致：
Even if I try to be consistent with Reads, and not Writes :
Cluster size: 2 / Replication Factor: 2 / Write Level: One / Read Level: Quorum
每次它告诉我我不能承受损失
Every time it tells me that I can't suffer the loss on any node.
推荐答案
那是因为复制因素
当复制因子超过节点数时，写入被拒绝，bu只要满足所需的一致性
水平，就可以进行t读。
来源： http://www.datastax.com/docs/1.0/cluster_architecture/replication
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