The data file with rows and columns, the bloom filter for the rows in the data file, the index for rows in the data file and the statistics.
Cheers ----------------- Aaron Morton Freelance Cassandra Developer @aaronmorton http://www.thelastpickle.com On 21 Jul 2011, at 23:26, Nilabja Banerjee wrote: > One more thing I want to ask here ...in the data folder of cassandra, for > each columnfamily four type of .db files are generated. for example: > CFname-f-1-Data.db, CFname-f-1-Filter.db, CFname-f-1-Index.db, > CFname-f-1-Statistic.db, > > What are these extensions are? > > Thank you > > > > On 21 July 2011 16:11, samal <sa...@wakya.in> wrote: > > Any ways , some where memtable has to be stored right, like we say memtable > data is flushed to create sstable on disk. > Exactly from which location or memory it will be getting from. is it like an > objects streams or like it is storing the values in commitlog. > > A Memtable is Cassandra's in-memory representation of key/value pairs. > > my next question is , data is written to commit log. all the data is > available here, and the sstable are getting created on disk, then where and > when these memtables are coming into picture > > Commitlog is append only file which record write sequentially, more[2], can > be thought as check sum file, which to used to recalculate data for memtables > in case of crash. > A write first hits the CommitLog, then Cassandra stores/writes values to > in-memory data structures called Memtables. The Memtables are flushed to disk > whenever one of the configurable thresholds is met.[3] > For each column family there is corresponding memtable. > There is generally one commitlog file for all CF. > > SSTables are immutable once written to disk cannot be modified. It will only > be replaced by new SSTable after compaction > > > [1]http://wiki.apache.org/cassandra/ArchitectureOverview > [2]http://wiki.apache.org/cassandra/ArchitectureCommitLog > [3]http://wiki.apache.org/cassandra/MemtableThresholds > >
