tell redis db to not persist

redis persists its memory data in snapshot style in every n seconds depending on your configuration.
read more here.
perhaps you would like to use redis as a pure in-memory db, like f.e. memchache.
you can tell redis to not persist and save some bits&miliseconds.
this could be the case when using redis as a f.e. realtime queue, you wont need persistence,
because you could say: nobody needs is newsfeed from the that day before the machine crashed ;)

alright, do so by:

open:
/etc/redis/redis.conf

you will find:

#   Note: you can disable saving at all commenting all the "save" lines.

save 900 1
save 300 10
save 60 10000

do as you are told:

#save 900 1
#save 300 10
#save 60 10000

…and save.
then restart redis.

sudo /etc/init.d/redis-server restart

Doing!