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Scylla SSTable Format

Sorted Strings Table (SSTable) is the persistent file format used by Scylla and Apache Cassandra. SSTable is saved as a persistent, ordered, immutable set of files on disk. Immutable means SSTables are never modified; they are created by a MemTable flush and are deleted by a compaction. The location of Scylla SSTables is specified in scylla.yaml data_file_directories parameter (default location: /var/lib/scylla/data).

SSTable 3.0 (mc format) is more efficient and requires less disk space than the SSTable 2.x. SSTable version support is as follows:

SSTable Version

Scylla Enterprise Version

Scylla Open Source Version

3.x (‘md’)


4.3 and above

3.0 (‘mc’)

2019.1, 2020.1

3.x, 4.1, 4.2

2.2 (‘la’)



2.1.8 (‘ka’)



  • In Scylla Enterprise 2021.1, Scylla 4.3 and above, md format is enabled by default.

  • In Scylla 3.1 and above, mc format is enabled by default.

For more information on each of the SSTable formats, see below: