NOSQL – Cassandra file structure – How is the file used?

/.../cassandra/ commitlog/CommitLog-.log
/.../cassandra/data/Keyspace1/Standard1-1-Data.db
/.../cassandra/data/Keyspace1/Standard1-1- Filter.db
/.../cassandra/data/Keyspace1/Standard1-1-Index.db
/.../cassandra/data/system/LocationInfo-1-Data.db
/.../cassandra/data/system/LocationInfo-1-Filter.db
/.../cassandra/data/system/LocationInfo-1-Index.db
/.../ cassandra/data/system/LocationInfo-2-Data.db
/.../cassandra/data/system/LocationInfo-2-Filter.db
/.../cassandra/data/system/ LocationInfo-2-Index.db
/.../cassandra/data/system/LocationInfo-3-Data.db
/.../cassandra/data/system/LocationInfo-3-Filter. db
/.../cassandra/data/system/LocationInfo-3-Index.db
/.../cassandra/system.log

/.../cassandra/commitlog/CommitLog-ID.log
/.../cassandra/data/KEYSPACE/COLUMN_FAMILY-N-Data.db< br />/.../cassandra/data/KE YSPACE/COLUMN_FAMILY-N-Filter.db
/.../cassandra/data/KEYSPACE/COLUMN_FAMILY-N-Index.db
/.../cassandra/system.log

Trying to use When Cassandra, I found that Cassandra will write the following files:

/.../cassandra/commitlog/CommitLog-.log
/ .../cassandra/data/Keyspace1/Standard1-1-Data.db
/.../cassandra/data/Keyspace1/Standard1-1-Filter.db
/.../cassandra/ data/Keyspace1/Standard1-1-Index.db
/.../cassandra/data/system/LocationInfo-1-Data.db
/.../cassandra/data/system/LocationInfo- 1-Filter.db
/.../cassandra/data/system/LocationInfo-1-Index.db
/.../cassandra/data/system/LocationInfo-2-Data.db< br />/.../cassandra/data/system/LocationInfo-2-Filter.db
/.../cassandra/data/system/LocationInfo-2-Index.db
/.. ./cassandra/data/system/LocationInfo-3-Data.db
/.../cassandra/data/system/LocationInfo-3-Filter.db
/.../cassandra/data/ system/LocationInfo-3-Index.db
/.../cassandra/system.log

The general structure seems to be:

/ .../cassandra/commitlog/CommitLog-ID.log
/.../cassandra/data/KEYSPACE/COLUMN_FAMILY -N-Data.db
/.../cassandra/data/KEYSPACE/COLUMN_FAMILY-N-Filter.db
/.../cassandra/data/KEYSPACE/COLUMN_FAMILY-N-Index.db 
/.../cassandra/system.log

What is the Cassandra file structure? More specifically, how is the data, commitlog directory used, and what is the structure of the files in the data directory (Data / Filter / Index)?

Writing to the Cassandra node first hits CommitLog (sequence). (Cassandra then stores the value in a column-specific memory data structure called Memtables. As long as one of the configurable thresholds is exceeded, Memtables will be flushed to disk. (1, datasize.2 in memtable, object’s #Reach a certain limit, 3, the validity period of the memory expires.))

The data folder contains subfolders for each key space. Each subfolder contains three kinds of files:

>Data file: SSTable (nomenclature
borrowed from Google) represents
sort string table and is a file
key-value string pair (Press. Sort)
key).
>Index file: (key, offset) pair (point to data file)
> Bloom filter: all keys in the data file