How to know the size of a keyspace and column family in Cassandra?

To get statistics regarding column families in Cassandra, you can simply run the command:

nodetool cfstats

It reports statistics about tables which include the live data size as well as on disk.

The documentation about this utility for Cassandra 2.1 is available here.

To get the statistics regarding column families in Cassandra with respect to keyspaces or tables, you can simply run the below command:

nodetool cfstats

Result: This will return the complete statistics related to available keyspaces.

But, in case you want to find out the statistics of specific keyspaces or tables, run below command:

For Keyspace(s) : nodetool cfstats <keyspace_name> OR nodetool cfstats -H <keyspace_name>

For Table(s) : nodetool tablestats <keyspace_name>.<table_name> OR nodetool tablestats -H <keyspace_name>.<table_name>

Note: -H denotes Human Readable format

For more details please refer, nodetool cfstats

Findings:

1. You might see SSTable count as 0

2. Space used (live) and Space used (total) as 0 bytes

To know WHY(s) of the above two findings please refer: Reason of why SSTable count shown as 0

I've created a small script to print nodetool results in a nice table:

#!/bin/sh
nodetool cfstats -H | awk -F ' *: *' '
  BEGIN { print "Keyspace,Table,Live,Total" }
  /^Keyspace : / { ks = $2 }
  /\tTable:/ { t = $2 }
  /\tSpace used .live/ { sp = $2 }
  /\tSpace used .total/ { print ks "," t "," sp "," $2 }
' | column -s , -t