Hi, My two-node cluster, run the following error after a period of time The server log: INFO [HintedHandoff:1] 2011-02-10 00:15:28,131 ColumnFamilyStore.java (line 952) Enqueuing flush of Memtable-HintsColumnFamily@2096038135(3281 bytes, 77 operations) INFO [FlushWriter:1] 2011-02-10 00:15:28,132 Memtable.java (line 155) Writing Memtable-HintsColumnFamily@2096038135(3281 bytes, 77 operations) INFO [CompactionExecutor:1] 2011-02-10 00:15:28,141 CompactionManager.java (line 272) Compacting [org.apache.cassandra.io.sstable.SSTableReader(path='/home/mengting/cassandra/data/system/HintsColumnFamily-e-109-Data.db'),org.apache.cassandra.io.sstable.SSTableReader(path='/home/mengting/cassandra/data/system/HintsColumnFamily-e-108-Data.db')] ERROR [CompactionExecutor:1] 2011-02-10 00:17:07,926 AbstractCassandraDaemon.java (line 91) Fatal exception in thread Thread[CompactionExecutor:1,1,main] ERROR [HintedHandoff:1] 2011-02-10 00:17:07,927 AbstractCassandraDaemon.java (line 91) Fatal exception in thread Thread[HintedHandoff:1,1,main] INFO [FlushWriter:1] 2011-02-10 00:17:07,988 Memtable.java (line 162) Completed flushing /home/mengting/cassandra/data/system/HintsColumnFamily-e-110-Data.db (2939 bytes) INFO [COMMIT-LOG-WRITER] 2011-02-10 00:17:07,989 CommitLog.java (line 470) Discarding obsolete commit log:CommitLogSegment(/home/mengting/cassandra/commitlog/CommitLog-1297186486611.log) Thanks