Hi, I have a cluster with two node servers（I know it’s in a wrong way but it‘s
builded by another colleague who has left）， and it's keyspace set like：
CREATE KEYSPACE my_keyspace WITH replication = {'class': 'SimpleStrategy',
'replication_factor': '3'} AND durable_writes = true;
one day my boss said one node was down for a long time and another worked
normally, tell my to restart the cluster.
First, I make a snapshot from the working node;
then, I check the data numbers with select count(*) cql statement, the result
is more then 170000;
Next, I add two new nodes. After new node worked, I use select count(*) cql to
check the data several times, but now I get uncertain resluts, and each reslut
is less then 10000; I check node status with ./nodetool status cql, and every
node is UN, but the load of two new nodes is far less then the normal node。
I stop the two new nodes, use “select count(*)” cql and get the right result
again.
I build a new cluster in sandbox env with snapshot file， and get the same
result like above。 I used "./nodetool repair" sql，then the cluster works well
but I don't know why.
I guess it because two nodes with "replication = {'class': 'SimpleStrategy',
'replication_factor': '3'} " can make splite brain and the data won't be
consistent，or the data file is broken but not make sure。Why did it happen, why
I have to use "./nodetool repair" command, and when to use it?
Thanks!
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赵豫峰
环信即时通讯云/研发
