I have a 25 noedes C* cluster with C* 2.1.3. These days a node occur split brain many times。
check the log I found this: INFO [MemtableFlushWriter:118] 2015-05-29 08:07:39,176 Memtable.java:378 - Completed flushing /home/ant/apache-cassandra-2.1.3/bin/../data/data/system/sstable_activity-5a1ff2 67ace03f128563cfae6103c65e/system-sstable_activity-ka-4371-Data.db (8187 bytes) for commitlog position ReplayPosition(segmentId=1432775133526, position=16684949) ERROR [IndexSummaryManager:1] 2015-05-29 08:10:30,209 CassandraDaemon.java:167 - Exception in thread Thread[IndexSummaryManager:1,1,main] java.lang.AssertionError: null at org.apache.cassandra.io.sstable.SSTableReader.cloneWithNewSummarySamplingLevel(SSTableReader.java:921) ~[apache-cassandra-2.1.3.jar:2.1.3] at org.apache.cassandra.io.sstable.IndexSummaryManager.adjustSamplingLevels(IndexSummaryManager.java:410) ~[apache-cassandra-2.1.3.jar:2.1.3] at org.apache.cassandra.io.sstable.IndexSummaryManager.redistributeSummaries(IndexSummaryManager.java:288) ~[apache-cassandra-2.1.3.jar:2.1.3] at org.apache.cassandra.io.sstable.IndexSummaryManager.redistributeSummaries(IndexSummaryManager.java:238) ~[apache-cassandra-2.1.3.jar:2.1.3] at org.apache.cassandra.io.sstable.IndexSummaryManager$1.runMayThrow(IndexSummaryManager.java:139) ~[apache-cassandra-2.1.3.jar:2.1.3] at org.apache.cassandra.utils.WrappedRunnable.run(WrappedRunnable.java:28) ~[apache-cassandra-2.1.3.jar:2.1.3] at org.apache.cassandra.concurrent.DebuggableScheduledThreadPoolExecutor$UncomplainingRunnable.run(DebuggableScheduledThreadPoolExecutor.java:82) ~[apache-cassandra-2. 1.3.jar:2.1.3] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) [na:1.7.0_71] at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:304) [na:1.7.0_71] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:178) [na:1.7.0_71] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [na:1.7.0_71] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [na:1.7.0_71] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [na:1.7.0_71] at java.lang.Thread.run(Thread.java:745) [na:1.7.0_71] I want to know why this and how to fix this Thanks all -------------------------------------- Ranger Tsao