Good idea to create a volume, so you can get an idea of the space consumption and how compression helps you:
maprcli volume create -name eoddata -path /user/vgonzalez/eoddata
Assuming you have installed log-synth to /opt, the following will create 10 million rows in 50 threads, with each thread producing a file:
/opt/log-synth/synth -schema eoddata.json -count $((10 * 10**6)) -format json -output /mapr/se1/user/vgonzalez/eoddata/2015-05-18 -threads 50