ruby on rails - Redis and Memcache or just Redis? -

i'm using memcached caching in rails 3 app through simple rails.cache interface , i'd background job processing redis , resque.

i think they're different enough warrant using both. on heroku though, there separate fees use both memcached , redis. make sense use both or should migrate using redis?

i using memcached caching because least used keys automatically pushed out of cache , don't need cache data persist. redis new me, understand it's persistent default , keys not expire out of cache automatically.

edit: wanted more clear question. know it's feasible use redis instead of both. guess want know if there specific disadvantages in doing so? considering both implementation , infrastructure, there reasons why shouldn't use redis? (i.e., memcached faster simple caching?) haven't found definitive either way.

assuming migrating memcached redis caching easy enough, i'd go redis keep things simple.

in redis persistence optional, can use memcached if want. may find making cache persistent useful avoid lots of cache misses after restart. expiry available - algorithm bit different memcached, not enough matter purposes - see http://redis.io/commands/expire details.