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In cassandra sstables are stored on disk and memtable are in cache so is there is 100% conversion from sstable to memtable i.e. if 10 GB of sstable is there then will it required 10 GB of ram ?

agrawal1084
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No that is not true. For better understanding check memtable related cassandra configuration, for example : memtable_heap_space_in_mb – This is the total allocated space for allmemtables on an Apache Cassandranode. By default, this is one-fourth your heap size. 

Also read about write and read path of cassandra.

Laxmikant
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  • Thanks Laxmikant. So does that mean for every read query first it checks into in memory memtable and then in sstable using bloom filter thats why read is slow relative to write as write are direcly flused to memtable and commit log. Out of curosity how does it know in memtable, is there is bloom filter for memtables also ? – agrawal1084 Jul 21 '18 at 04:18
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    bloom filter in cassandra is related to sstables only and not memtables as in memory reads are already very fast. For more info check this link https://docs.datastax.com/en/cassandra/3.0/cassandra/dml/dmlAboutReads.html – Laxmikant Jul 21 '18 at 10:25