Bitcask, fill the key storage memory up by continously storing lots of objects with big keys and small data.
while true ;
do echo run ;
curl -XPUT -H "Content-Type: application/text" -d 'foo' "http://127.0.0.1:8098/riak/default/test$(date +"%s")${RANDOM}${RANDOM}$(seq 1 2200 | tr -d '\n') " ;
done