Storage

When a table is created on MariaDB ColumnStore, the system creates at least one file per column for the table. So, for example, a table created with three columns would have at a minimum, three separately-addressable logical objects created on a SAN or a server’s disk drives.

• Each column is stored independently in 8M rows logical measure called an Extent. An extent for 1 byte datatypes consume 8MB; 2 byte datatypes consume 16MB; 4 byte datatypes consume 32MB; 8 byte datatypes consume 64MB; and variable size datatypes consume 64MB. Once an extent becomes full, a new extent is automatically created.
• An Extent is physically stored as collection of blocks.
• A block is 8K Bytes. Every database block in a database is uniquely identified by its Logical Block Identifier (LBID)
• String columns > 8 characters store indexes in the main column file and actual values in separate dictionary files.
• A segment file is a physical file on disk that holds a column’s data. Once a segment file reaches its maximum number of extents, a new segment file is automatically created
• Collectively, all the column's segment files for one ore more extents form a Partition
• Partitions are stored in a hierarchical structure organized by segments (i.e. folders)
• MariaDB ColumnStore meta-store maps file structure/location to DB schema as well as information used for partitioning
• By default the data is compressed