Hi, I have a column family/ table that has frequent update on one of the column, and one column that has infrequent update. Rest of the columns never changed. Our application also read frequently on this table.
We have seen some read latency issue on this table and plan to switch to use level compaction on this table. Few questions: #1 In Cassandra Server JMX, there is "readcount" attribute, what is consider a read? accessing a row will consider a read count? #2 For JMX "read latency", does it include consistency level (fetching data from other nodes) or coordinator related work load? #3 >From the doc, level compaction stated it will guarantee that all sstables in same level are 'non-overlapping", what does it really mean? (trying to visualize how this can reduce read latency) #4 If I change my select CQL query not to include the frequently changed column, will that improve read latency? #5 How significant of the improvement of change compaction from sized to level? is it day and night difference? and it is true that while sized compaction latency will get worse, level compaction can give very consistent read latency for long long time? Thanks
