sstablesplit

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.

ref: https://issues.apache.org/jira/browse/CASSANDRA-4766

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

Usage

sstablesplit <options> <filename>

–debug	display stack traces
-h, –help	display this help message
–no-snapshot	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.

Example:

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.

Example:

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.

Example:

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.

Example:

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.

Example:

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.