Cassandra Documentation



Big sstable files can take up a lot of disk space. The sstablesplit tool can be used to split those large files into smaller files. It can be thought of as a type of anticompaction.

Cassandra must be stopped before this tool is executed, or unexpected results will occur. Note: the script does not verify that Cassandra is stopped.


sstablesplit <options> <filename>

--debug display stack traces

-h, --help

display this help message


don’t snapshot the sstables before splitting

-s, --size <size>

maximum size in MB for the output sstables (default: 50)

This command should be run with Cassandra stopped. Note: the script does not verify that Cassandra is stopped.

Split a File

Split a large sstable into smaller sstables. By default, unless the option --no-snapshot is added, a snapshot will be done of the original sstable and placed in the snapshots folder.


sstablesplit /var/lib/cassandra/data/keyspace/eventlog-6365332094dd11e88f324f9c503e4753/mc-8-big-Data.db

Pre-split sstables snapshotted into snapshot pre-split-1533144514795

Split Multiple Files

Wildcards can be used in the filename portion of the command to split multiple files.


sstablesplit --size 1 /var/lib/cassandra/data/keyspace/eventlog-6365332094dd11e88f324f9c503e4753/mc-1*

Attempt to Split a Small File

If the file is already smaller than the split size provided, the sstable will not be split.


sstablesplit /var/lib/cassandra/data/keyspace/eventlog-6365332094dd11e88f324f9c503e4753/mc-8-big-Data.db
Skipping /var/lib/cassandra/data/keyspace/eventlog-6365332094dd11e88f324f9c503e4753/mc-8-big-Data.db: it's size (1.442 MB) is less than the split size (50 MB)
No sstables needed splitting.

Split a File into Specified Size

The default size used for splitting is 50MB. Specify another size with the --size option. The size is in megabytes (MB). Specify only the number, not the units. For example --size 50 is correct, but --size 50MB is not.


sstablesplit --size 1 /var/lib/cassandra/data/keyspace/eventlog-6365332094dd11e88f324f9c503e4753/mc-9-big-Data.db
Pre-split sstables snapshotted into snapshot pre-split-1533144996008

Split Without Snapshot

By default, sstablesplit will create a snapshot before splitting. If a snapshot is not needed, use the --no-snapshot option to skip it.


sstablesplit --size 1 --no-snapshot /var/lib/cassandra/data/keyspace/eventlog-6365332094dd11e88f324f9c503e4753/mc-11-big-Data.db

Note: There is no output, but you can see the results in your file system.