[ https://issues.apache.org/jira/browse/CASSANDRA-9274?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Donald Smith updated CASSANDRA-9274: ------------------------------------ Description: It says in cassandra.yaml: {noformat} # If your data directories are backed by SSD, you should increase this # to the number of cores. #memtable_flush_writers: 8 {noformat} so we raised it to 24. Much later we noticed a warning in the logs: {noformat} WARN [main] 2015-04-22 15:32:58,619 DatabaseDescriptor.java:539 - memtable_cleanup_threshold is set very low, which may cause performance degradation {noformat} Looking at cassandra.yaml again I see: {noformat} # memtable_cleanup_threshold defaults to 1 / (memtable_flush_writers + 1) # memtable_cleanup_threshold: 0.11 #memtable_cleanup_threshold: 0.11 {noformat} So, I uncommented that last line (figuring that 0.11 is a reasonable value). Cassandra.yaml should give better guidance or the code should *prevent* the value from going outside a reasonable range. was: It says in cassandra.yaml: {noformat} # If your data directories are backed by SSD, you should increase this # to the number of cores. #memtable_flush_writers: 8 {noformat} so we raised it to 24. Much later we noticed a warning in the logs: {noformat} WARN [main] 2015-04-22 15:32:58,619 DatabaseDescriptor.java:539 - memtable_cleanup_threshold is set very low, which may cause performance degradation {noformat} Looking at cassandra.yaml again I see: {noformat} # memtable_cleanup_threshold defaults to 1 / (memtable_flush_writers + 1) # memtable_cleanup_threshold: 0.11 #memtable_cleanup_threshold: 0.11 {noformat} So, I uncommented that last line (figuring that 0.11 is a reasonable value). Cassandra.yaml should give better guidance or the code should *prevent* the value from going outside a reasonable range. {noformat} > Changing memtable_flush_writes per recommendations in cassandra.yaml causes > memtable_cleanup_threshold to be too small > ----------------------------------------------------------------------------------------------------------------------- > > Key: CASSANDRA-9274 > URL: https://issues.apache.org/jira/browse/CASSANDRA-9274 > Project: Cassandra > Issue Type: Improvement > Reporter: Donald Smith > Priority: Minor > > It says in cassandra.yaml: > {noformat} > # If your data directories are backed by SSD, you should increase this > # to the number of cores. > #memtable_flush_writers: 8 > {noformat} > so we raised it to 24. > Much later we noticed a warning in the logs: > {noformat} > WARN [main] 2015-04-22 15:32:58,619 DatabaseDescriptor.java:539 - > memtable_cleanup_threshold is set very low, which may cause performance > degradation > {noformat} > Looking at cassandra.yaml again I see: > {noformat} > # memtable_cleanup_threshold defaults to 1 / (memtable_flush_writers + 1) > # memtable_cleanup_threshold: 0.11 > #memtable_cleanup_threshold: 0.11 > {noformat} > So, I uncommented that last line (figuring that 0.11 is a reasonable value). > Cassandra.yaml should give better guidance or the code should *prevent* the > value from going outside a reasonable range. -- This message was sent by Atlassian JIRA (v6.3.4#6332)