Graylog2 System Requirement

If you’re running all components (Graylog, Elasticsearch, MongoDB) on a single machine, a reasonably modern multicore CPU and 4 GB of main memory will do it.

Graylog itself will also run on a machine with 1 or 2 GB of main memory.

As always: The more the better (i. e. more main memory, faster CPU with more cores, SSD instead of spinning rust).